gaga, n.² — Green’s Dictionary of Slang

gaga n.²

[? play on the ga-ga noises of babytalk or gaga adj. (2)]

(US gay)

1. an inexperienced, immature homosexual.

1941		G. Legman ‘Lang. of Homosexuality’ Appendix VII in Henry Sex Variants.
1947		(con. 1944) J.H. Burns Gallery (1948) 139: Now Enzo led the life of a gaga, strolling the town in a T-shirt, inviting his friends to coffee in the afternoon, and singing at dusk in dark corners. [...] Over his shorts he wore shirts of scented silk or pongee.
1965		Guild Dict. Homosexual Terms 18: gaga (adj., n.): [...] (2) An inexperienced, immature homosexual.

2. homosexual foreplay.

1965

Guild Dict. Homosexual Terms 18: gaga (adj., n.): [...] (3) The first steps of arousal between two homosexuals who enjoy each other’s intimacy.