Lillian Morrison was obviously enjoying herself as she held court with a group of wide-eyed teen-agers. Her own eyes sparkled and her hands danced as she shared her experiences with them.

Despite the gray hair peeking out from under her floppy hat, Morrison spoke the language of the young. Throughout the afternoon the group relived her experiences in the Women's Army Corps in World War II and marched with her to halt the Vietnam war. Later they learned what it was like to be 18 and living alone when bread was nickel and young, unmarried mothers were branded "ruined!"

"What do you think of living together?" the teens asked.

"It's perhaps more realistic than dating," said Morrison to the their obvious surprise. "In dating you're always on your best behavior."

As they talked, the gulf between the generations began closing. The phenomenon was also happening elsewhere as similar groups of teens and senior citizens met recently at the National Presbyterian Church to compare notes about their personal experiences. The rap session, billed as a "Generation Gap Rap," was sponsored by the Iona House Community Service Center and covered six basic topics ranging from adolescence to death.

In addition to the topics pre-selected by a committee of students and senior citizens, the 120 participants int he Gap Rap debated subjects like teen-age marriages, abortion, unwed motherhood, the war years and living together.

As the Morrison group discussed issues relating to their adolescent years, Elizabeth Fulton, a senior citizen and Sally Rubin, an 18-year-old junior at Sidwell Friends High School, moderated a discussion on death.

"The one experience everybody shares is the actual dying experience," said student Robert Spencer.

Janet Neuman, a white-haired, matriarchal figure who is active in the Gray panthers, a senior citizens lobby group, agreed.

"I'm 83, and at 83 you know perfectly well you days are numbered," she remarked.

The group talked about the deaths of parents, friends, spouses and other loved ones including pets. As they discussed their fears and expectations about dying they seemed to unite closer in life. Perhaps because, as senior citizen William Guiler explained in his greeting to the participants, "Understanding comes through communication."

Students at the session said they felt they weren't exposed to senior citizens as much as they should be; furthermore, they didn't know where to find any.

"My neighborhood is all young people with little children," said Laury MacIntosh, 17, a junior at Walt Whitman High School.

Sally McCarthy, assistant director of Iona House, said the overall purpose of the rap session was to promote exposure and communication between senior citizens and young people.Most of the seniors were from Iona House while the young people came from five area junior and senior high schools. Iona House held a similar rap session two years ago, she said.

Iona House, located at 4200 Butterworth Place NW, is a private, non-profit community service group aiding the elderly and the widowed in the Washington community. The service is supported financially by eight area churches.

A senior recreation program meets Tuesdays and Thursdays from 11 a.m. until 3 p.m. A telephone reassurance service and visitors group is also in operation to help homebound elderly. The widow-to-widow program allows trained aides, themselves widows, to visit citizens coping with the loss of a spouse.