Green’s Dictionary of Slang

cheating, deceitful.

1916		A. Stringer Door of Dread 84: Hand it to the corn-rustlers who ain’t hep to a crook from the gyp-game days! For it don’t go wit’ me! I know who yuh are.
1921		N.Y. Trib. 3 July 48/6: That is a sample of the genuine Coney Island gyp stuff.
1922–24		O.O. McIntyre White Light Nights 34: The rest will follow blindly. [...] No matter whether the trail leads to a gypping cafe or a signless shop where clerks drop their h’s.
1927, 1932, 1970, 1985, 2004		implied in gyp joint under gyp n.1
1933		W.R. Burnett Dark Hazard (1934) 64: I never had much time for dogs or dog-men. It’s a gyp racket.
1949		L. Hughes Tambourines to Glory II v: Religion’s got no business being made into a gyp game.
1961		T. Williams Night of the Iguana Act I: The gyp touch, the touch of a de-frocked minister is running a gyp nudist gym on the South Side.
1962		C. Clausen I Love You Honey, But the Season’s Over 153: Carnie talk originated in the early carnivals, and was used by the men who ran the gyp games to signal to each other that a cop was coming or that a sucker was catching on.