Remember when "gay" used to mean something like "merry" or "jolly?" In that sense, as well as the one that has superseded it, Saturday was an extraordinarily gay evening in the Kennedy Center Concert Hall. For 3 1/2 hours, the Anita Bryant jokes flowed like orange juice, the entertainment fully justified the rather hefty admission prices and the politicking (chiefly by the redoubtable Gloria Steinhem) was kept eloquent but low-key.

It was the "Encore for Freedom," sponsored by an ad-hoc organization called Dialog for Human Rights, and besides providing a good time for all it raised around $20,000 to be divided among the Gay Activists Alliance, the Gertrude Stein Democratic Club and the National Organization for Woman.

The political motif of the evening was stated most succinctly by Steinem, who noted that "Leonardo da Vinci would not be allowed to teach school in Dade County," and by master of ceremonies Tom Gauger of WMAL radio, who got a large response to his announcement of a "Stop Anita Bryant" rally next Saturday in Richmond. The entertainment (songs by a variety of performers, comic skits by a group called Red Shoes Walkin' and a brief, hilarious visit by Gotham between their shows at The Cellar Door) was generally excellent, but the real star of the evening (all the performers said so) was the audience.

The atmosphere was like that which can be sensed sometimes at gay theaters and cabarets - a room full of people who usually feel that they have to be careful, whom society douses regularly and liberally with the idea that they don't belong, enjoying a few hours in an atmosphere where their attitudes are the norm, where they are accepted and where they can relate fully, enthusiastically to what is happening. There were very real if intangible vibrations in the air, expressed mainly in the spontaneous, warm and generally well-earned applause, the interplay between performers and audience, the sense almost of family that filled the place. The difference is that such theaters and cabarets are relatively small places; the Concert Hall is enormous and it was filled almost to capacity.

Like other collective descriptions ("Republican," for example, or "black" or "Episcopalian"), the term "homosexual" and its many synonyms lump together a bewildering variety of people who have a few things in common and many qualities that are purely individual and more important. The outsider looking for a cheap shock could have found it during intermission: a few ladies in mannish suits and a half-dozen drag queens spectacular in full regalia - hairdos and gowns that any woman in Washington might envy and a pure physical presence that was statuesque, handsome, striking as a virtuoso dramatic performance.

But most of the audience was unremarkable except for the predominance of conservatively dressed, soft-spoken young men who were there to have a good time and perhaps to suggest that they, too, deserve the full protection of law. Seen a few at a time, they would be taken for granted; when there are thousands all together, the impact is a bit disorienting for the average straight.

After a few opening jokes by David Kopay, the show began with its only really disappointing act, Lyn Frizzell, who sand his notorious "Hurricane Anita" and a new song about a local celebrity entitled "Moore or Less." Frizzell has evidently a tricky way with lyrics, but his microphone technique on this occasion made that talent hard to appreciate, at least near the front fo the Concert Hall. Beyond a few disconnected phrases, the only coherent lines that came through clearly were "More or less, we need less of Moore" and (in another song) "We're so glad that you're coming out."

Two singers on the program had extraordinary voices: Barbara Cook, whose tone really blossoms in the vast spaces of the Concert Hall and Granger, who ended up leading a sing-along "America the Beautiful" after a fine mixture of classical and popular numbers that included (in sequence) the "Segurdilla" from "Carmen," "Birth of the Blues," "Can't Help Lovin' That Man" and "When he Saints Go Marching In."

The main surprise of the evening for me - since I'm not plugged into the underground Lesbian musical circuit - was Casse Culver and the Belle Starr Band, a talent I would not hesitate to compare to Emmylou Harris. Culver writes songs as well as she sings them and her lyrics and style most of the time should appeal strongly to the general public.

Most of the evening's pure comedy was provided by Red Shoes Walkin,' a mixed quartet of improvisational actors and by Gotham, a trio which hardly needs and introduction to Washington audiences by now. RSW's two routines (both involving imitations of Anita Bryant) were of special interest to pay people, but obviously theirs is a collective talent that can and will win a much wider audience.