Ronald Reagan's counselor, Edwin Meese III, yesterday gave what may be the ultimate in laid-back description of nuclear war. He called it "something that may not be desirable."

Meese was addressing the Civil Defense Association at the Shoreham Americana Hotel, bearing the president's warm good wishes and the happy news that Reagan intends to double its budget as part of his strategic planning.

Meese conceded that it is "not an easy task to defend and justify civil defense" because "it is the kind of thing people have a psychological aversion to."

Reagan's plans to add 17,000 nuclear warheads to an arsenal of 25,000 has run into considerable flak. Aroused physicians and scientists are raising the alarm about unspeakable death and destruction. The American Medical Association has formally declared that "no medical response" is possible in the event of nuclear attack. And Jonathan Schell's New Yorker series about the end of the planet is working its way into the national psyche.

But Meese said that that civil defense "is a deterrent for a possible attack on this nation" and the Civil Defense Association workers applauded vigorously.

"Preparedness," he declared, "is the best way to avoid the consequences of something that may not be desirable."

The "deterrent," as presently constituted, seems unlikely to give the Soviets pause. At its heart is the crisis relocation plan, an intricate, upbeat scheme that envisions orderly removal of citizens from "target areas" to "host areas" and their return, within a relatively short period of the bomb burst--a return to "a home area" that sounds a step away from normalcy.

A few lines from the literature put out by the Federal Emergency Management Agency, which is in charge of civil defense, from a section called "What Home May Be Like" give the flavor of this exceptionally sunny scenario:

"Fuel and food supplies will be rerouted to your home area; however, this may take a day or two . . . . It may be necessary to take extra precautions with waste. Some food stocks will probably have to be carried back in your car. Be sure it is fresh, particularly raw meat."

The whole thing conjures up a picture of an area that has somehow escaped flattened buildings, heaped corpses and the radiated, blinded, or burned inhabitants generally associated with nuclear assault.

The real defect in the plan is that it relies on an eight-day warning which, according to William Murray, public affairs director of the Civil Defense Association, "we will not receive."

But Meese says that "reinvigoration" of civil defense will "give people the confidence that their lives can be protected."

The Civil Defense workers might have benefited more from listening to one of their number who was not at yesterday's meeting. Perhaps the speech given to the Greensboro, N.C., City Council by Marilyn Braun, 37, coordinator of the Greensboro-Guilford Emergency Management Assistance Agency, would have been more to the point.

Braun, charged by her superiors with making a two-year update of war plans, sent instead a letter of protest which, she was told, would "never get to the federal level." But to avoid a fuss, these superiors accepted her protest as an update and confined themselves to complaining to reporters that she is "uncooperative."

Upon presenting the findings of a committee of experts and concerned citizens who studied all aspects of the problem, she told the Greensboro City Council on Feb. 11:

"We have no protection today in Greensboro or Guilford County for this threat . . . the documents and civil defense publications that we have on record fail to address minimal human needs in protecting people from 'blast' and 'fallout' . . . . Given these circumstances, we are presently unable to design an emergency plan to offer protection from nuclear detonations. We do not think it can be done in Greensboro and Guilford County, and we do not think it has been done in any other city or county in the U.S."

Braun, who has become somewhat of a heroine in anti-nuclear circles, speaks very softly on the telephone. She also takes direct action. She removed the "fallout shelter" signs from the 170 buildings so designated by FEMA because, she said, they do not offer shelter from radiation or starvation.

Braun's regional superiors have warned her that her federal funds may be cut off if she does not adopt a more positive attitude. One third of the Guilford-Greensboro allowance comes from Washington, which expects its share to be used for nuclear war planning.

Braun thinks that "as long as people have an illusion of protection, it may very well stand in the way of thinking about the threat."

But at the White House, the illusion is strong.

That's why the man closest to the president can talk about nuclear war not as the last call for the planet but merely as "something that may not be desirable."