Green’s Dictionary of Slang

1. an orgy.

1968		G. Legman Rationale of the Dirty Joke (1972) I 93: A brief and permissive publicty reference to the hippies’ ‘group grope’.
1971		E. Wilson Show Business Nobody Knows 369: [A] ‘group grope,’sort of a minor orgy, a community feel, with everybody hand-massaging everybody while piled together naked on the floor.
1979		Maledicta III:2 232: He also may or may not know the following words and expressions: [...] gang bang (group grope, orgy, or gang rape).
1997		Solar Project ‘Zeitgest’ 🎵 on ...in Time [album] Group grope, bunch punch / Gang bang, daisy chain / Leg work, Swedish culture, S & M / We are shagging like wild rattlesnakes / We bang like the shithouse door in a gale.
2000		M. Orth Vulgar Favors 366: Once the foam reaches waist level, the scene becomes group grope in the suds of a giant bubble bath.

2. (US campus) in fig. use, an encounter group, esp. one that stresses physical contact.

1973		Eble Campus Sl. Mar. 2: group gropes – encounter groups.
1978		N.Y. Rev. of Books 26 Jan. 22: It’s a group grope at Esalen [...] an orgy of touching, palpating, feeling, stroking.
1993		A. Synnott Body Social 176: Some critics have denounced the movement as ‘group-grope’ or ‘touchy feely’.
1996		Eble Sl. and Sociability 42: Alliteration marks [...] group gropes ‘encounter groups’.