Green’s Dictionary of Slang

1. (US) clever in a showy way.

1929		C. Coe Hooch! 230: Then you come around and try to run the wise-guy racket on me.
1935		(con. 1920s) J.T. Farrell Judgement Day in Studs Lonigan (1936) 749: Studs decided he was a wise-guy bastard.
1937		R. Westerby Wide Boys Never Work (1938) 123: I’m sick of this wise-guy stuff of yours.
1947		Gloucs. Echo 30 Sept. 3/6: Dave Fenner, irritating wise-guy crime reporter, is likably portrayed by [etc.].
1955		E. Hunter Blackboard Jungle 197: Just keep your smart-guy language to yourself. [Ibid.] 225: You’ve got a nerve to ask that! [...] After your goddamn wise-guy remarks, and after the way you fouled up that lesson.
1962		(con. 1940s) G. Mandel Wax Boom 157: Boy, you been talking an awful lot of wise-guy stuff.
1971		J.D. Horan Blue Messiah 120: Just a little wise guy mocky.
1987		T. Wolfe Bonfire of the Vanities 121: A wiseguy liquor distributor who routinely cut costs by hijacking merchandise.
2000		F. Kellerman Stalker (2001) 99: She was about to blurt out a wiseguy comment, but it stuck in her throat.

2. (US) related to the US Mafia or its culture and lifestyle.

1952		(con. 1910s) ‘Harry Grey’ Hoods (1953) 5: In wise-guy fashion he spoke through the corner of his mouth.
1979		E. Torres After Hours 124: They go to a wise-guy joint.
1985		N. Pileggi Wiseguy (2001) 99: The big bills were just too much trouble for wiseguy bookmakers to cash.
1994		G. Disher Crosskill [ebook] Victor’s Las Vegas wiseguy mates would rake off all the profits.
1996		S. Frank Get Shorty [film script] chili: I’m thinking of a movie. martin: One of mine? chili: One we’re producing. martin: With what? Wiseguy money?
2010		(con. 1973) C. Stella Johnny Porno 76: Bridget Malone was working off her end of the heroin bust gathering information against her wiseguy boyfriend.
2019		D. Winslow Border [ebook] [A] lot of independent dealers [...] buying from wiseguy retailers who buy it from the mills uptown.