In Spanish, the word contra is shorthand for "counterrevolutionary," and when the small band of escaping and self-exiled Nicaraguan soldiers and businessmen began their struggle to overthrow Nicaragua's ruling Sandinistas more than five years ago, that was what the Sandinistas called them.

Partisans of Nicaraguan dictator Anastasio Somoza, they had been opposed to the Sandinista National Liberation Front as soon as it launched a civil war in late 1978. After the leftist Sandinistas won in July 1979, ousted Somoza and established their new "revolutionary" government, it was only a matter of days before the "counterrevolutionaries" launched their first operations.

Enormous changes have taken place since that early band began attacking the Sandinistas and their Cuban advisers. Thousands of initially prorevolution Nicaraguans now are disenchanted with Sandinista rule and have become rebel recruits. With funds, guidance and sustained impetus from the Reagan administration, the anti-Sandinista rebels have become a guerrilla army to be reckoned with.

Yet as the shooting war has grown, it has been matched, battle for battle, by a propaganda war over whether these guerrillas are being led by the same old pro- Somoza contras -- as the Sandinistas maintain -- or are, as President Reagan has described them, a force of anti-Marxist "freedom fighters."

Both the rebel leaders and the vast majority of their foot soldiers are not pro-Somoza but are former "revolutionaries" themselves, the administration and rebel leaders have said. Continued rebel efforts to stop the Sandinistas from exporting their revolution and to pressure them to become more democratic, they have maintained, are vital not only to Nicaragua, but ultimately to American freedom itself.

It is on this distinction, along with a feeling among some congressmen that the United States should not be funding a "secret war" against a sovereign nation nor supporting a guerrilla army no matter what it is called, that the future of U.S. funding for the rebels partly depends.

During the past three years, since Reagan first authorized money and support for the guerrillas, the not-so-secret war against the Sandinistas has taken its toll on the organization charged with supervising it -- the Central Intelligence Agency. A number of U.S. intelligence veterans of the anti-Sandinista operation say they believe that it has gone on too long, too publicly, too cheaply and with too little direction or results.

But continuing difficulties in the war, for both the CIA and the rebels, according to U.S. intelligence and rebel sources, have been matched by problems in propaganda and what might be called the "organizational" war to define and lead the anti-Sandinista army.

With Congress reluctant to renew U.S. funding for the rebel cause, and with the administration trying to decide what to do if Congress refuses, the guerrillas in Nicaragua and their leaders in Honduras and the United States appear to have reached a crucial moment in their struggle.

Insurgent leaders insist that they can carry on the fight with funds from other sources, as they have since CIA financing dried up on congressional orders last June. But with the fortunes required to run a guerrilla war, particularly against improved Sandinista armaments, the outcome in Washington is likely to have a decisive effect on the thousands of Nicaraguans who have put their lives and livelihoods on the line against what they regard as the intolerable regime in Managua. Birth of an Army

Although roving bands of former Somoza soldiers began their war against the Sandinistas soon after the dictator's ouster in 1979, the organization of the rebels into a real guerrilla army with real possibilities did not begin until the onset of U.S. funding in late 1981.

Since that time, although the structure of political leadership has shifted both here and in Honduras, the anti-Sandinista movement has retained a consistent military commander, Enrique Bermudez. With his ranks grown sharply in part because of $80 million in U.S. funds during the past three years, the determined former officer of Somoza's National Guard in charge and the youths who have made roadside ambushes their way of life appear to have little reason to abandon their commitment on considerations defined in Washington.

According to rebel leaders and witnesses, most of the rebel combatants are young peasants and small landowners bothered by zealots dispatched by Sandinista rulers in Managua to reform the conservative backlands of coffee plantations and tobacco farms. Many also come from families that included soldiers in the National Guard, which they say constitutes a stain in the eyes of Sandinista authorities and many other Nicaraguans who consider the guard a symbol of Somoza's oppression.

Rebel officials say the combatants are led by about 10 regional commanders, each in charge of several "task forces," including one named after Jeane J. Kirkpatrick, U.S. ambassador to the United Nations. Except for a leader known in the movement only as "Tigrillo," who fought on the side of the Sandinistas before their victory in 1979, the most prominent commanders gained military experience as soldiers or officers in the National Guard, rebel sources say.

For some, this was supplemented by training in Argentina in 1981, before CIA advisers took a direct hand in running the rebellion, according to Edgar Chamorro, an insurgent leader expelled from the organization last month in a dispute with his colleagues.

The composition of rebel forces has been an important public relations point from the beginning. While they acknowledge the rebels' peasant following in private, Sandinista officials speaking publicly in Managua depict the insurgency as an enterprise of National Guard and Somoza revanchists directed by CIA advisers carrying out orders from Reagan to topple the government.

To counter this, rebel leaders insist that only 2 percent of guerrilla ranks are filled by former National Guard troops and stress that they could not remain in the country without support from the people. In addition, they seek to conceal the key role played by former National Guard officers in the top military command operating in Honduras with cooperation from the Honduran military. Rebel Reorganization

It was partly this concern that prompted CIA advisers in late 1982 to organize a new overall leadership for the main insurgent group, the Nicaraguan Democratic Force, FDN by its Spanish initials, according to Chamorro and several other rebel activists who say they were interviewed as likely prospects by CIA agents here and in Washington. Chamorro, who trained to become a Jesuit priest, joined then as part of what he describes as a "repackaging" of the rebel movement for the U.S. Congress and public, eliminating leaders tied to Somoza from public view.

Until the reorganization announced in December 1982, the FDN leadership comprised Jose Francisco "Chicano" Cardenal, a Managua contractor who had served in the Sandinista Council of State until he abandoned the revolution and settled in Miami; Mariano Mendoza, a former union organizer also disenchanted with the revolution; Aristides Sanchez, a landowner connected to Somoza socially before 1979 and to Somoza followers who fled to Miami afterward, and seven former National Guard officers: Bermudez, Emilio Echaverry, Edgard Hernandez, Ricardo Lau, Manuel Caceres, Francisco "El Gato" Rivera and Juan Gomez.

Bermudez, who was military attache in Washington under Somoza, had served along with Sanchez on the governing junta of the 15th of September Legion. This small group of former military men, with Bermudez as their leader, launched early sabotage raids against the Sandinista government. It merged with other small groups, including political alliances in Miami, to form the FDN, with Cardenal as a visible leader and Bermudez remaining as operational leader working with Argentine advisers in Honduras.

The decision of Argentine and CIA advisers to work with Bermudez meant the death of other efforts to organize a large insurgent force. Pedro Ortega, a Spanish-born owner of a match factory under Somoza, dropped out after spending what he said was a million-dollar personal fortune to send guerrillas along Nicaragua's Caribbean coast. Edmundo Chamorro, another early leader who sought Argentine support, was passed over.

The focus of attention and money on Cardenal and Bermudez set a pattern that has continued and intensified as the insurgency has grown from 500 men based in Honduras in 1981 to what their leaders now maintain are more than 12,000, most of them in Nicaragua. While Cardenal dealt with governments, including the Reagan administration, Bermudez worked quietly and directly with foreign advisers and suppliers to run the actual guerrilla war.

As military attache in Washington and commander of Somoza's contingent within the Organization of American States forces during the U.S.-led invasion of the Dominican Republic in 1965, Bermudez had the opportunity to make key acquaintances in the U.S. military and intelligence establishments. Echaverry, his main aide, had attended military courses in Argentina along with Gen. Gustavo Alvarez, then head of the Honduran military, who along with Argentine and U.S. officials made Honduras a haven for the insurgents.

Significantly, Bermudez was the only FDN leader to remain in the "repackaged" FDN National Directorate of December 1982. Although politically attractive as an anti- Somoza activist and former offical under the Sandinistas, Cardenal was dropped at the insistence of Argentine advisers who were directing the insurgents in Honduras, according to FDN officials.

The dispute revolved around Cardenal's efforts to act as leader, with Argentine officers insisting on retaining control of the insurgency, Edgar Chamorro recalled. Col. Osvaldo Ribeiro, a commander of the Argentine advisers group, personally handed out funds to rebel leaders and went so far as to give Cardenal personal expense money in humiliatingly small weekly amounts, he added.

At that time, CIA advisers were playing a secondary role in Honduras and were rarely seen there before guerrilla ranks began to grow in 1983, Chamorro said. Ribeiro traveled occasionally to Washington and Miami, but U.S. officials were the main contacts in the United States, he declared.

With Bermudez and Chamorro on the new FDN leadership panel were Lucia Cardenal, widow of a slain and highly respected business leader; Marco Zeledon, a Managua business organizer who once served in the U.S. Army; Indalecio Rodriguez, a university rector who was among the original members of the Sandinista National Liberation Front, and Alfonso Callejas, a minister and vice president under Somoza. Adolfo Calero, a silver-haired businessman who once managed Nicaragua's Coca-Cola plant, joined the group later and emerged with the title of commander in chief as rebel forces grew through 1983. New Leaders Opposed Somoza

Except for Bermudez and Callejas, the new leaders all had been active in the struggle against Somoza. Calero was jailed by the National Guard for organizing business opposition to the government, and Zeledon played a key role in fomenting a crucial anti-Somoza national strike. Their pasts, along with similar anti-Somoza activities by Chamorro and Rodriguez, were underlined in appeals for U.S. and Nicaraguan public support.

Immediately under Bermudez on his military staff, however, were some of the same National Guard officers who had helped start the insurgency. They included Echaverry, still working closely with his classmate Alvarez; Lau, in charge of counterintelligence; Gomez, in charge of the rebel "air force"; Caceres, and Hernandez.

In addition, according to Chamorro, top officers included Justiciano Perez, who before 1979 was second in command under Somoza's son at the Basic Infantry Training School, and Hugo Viagra, who was named "operations theater commander" but was dismissed in a command shake-up late last year. Sanchez, who is related to Calero by marriage, became National Directorate secretary and one of Calero's closest aides.

Bermudez, Lau and Perez particularly have been cited by followers of Eden Pastora as reasons for his refusal to join forces with the FDN -- on the ground that it remains under control of National Guard officers, against whom Pastora fought during the Sandinista revolution.

After fighting last year in collaboration with Alfonso Robelo in the Costa Rican-based Revolutionary Democratic Alliance, ARDE, Pastora has gone his own way since the summer because of Robelo's decision to join with the main FDN. Without funds for ARDE military efforts, now commanded by Fernando "El Negro" Chamorro, Robelo has decided to concentrate on political activities, Calero reports. Pastora, also without financing since the CIA cutoff last summer, has gone his own way with several thousand mostly inactive guerrillas along the Nicaraguan-Costa Rican border.

In an effort to attract the politically popular Pastora last spring, Calero's FDN leadership announced that it had trimmed National Guard officers from the top command. Lau and Perez in particular were said to have left the rebel organization.

Other insurgent officials say, however, that Perez remains active as a military aide to Steadman Fagoth, leader of Miskito Indian forces allied with the FDN, and Lau also is still on hand in Honduras working as before to prevent Sandinista attacks or infiltrations.