Green’s Dictionary of Slang

(US) superb, magnificent, excellent, usu. show business use.

1944		Advertising & Selling 37 1-6 41/2: She has made Cosmo boffo b.o.
1947		Phila. Eve. Bulletin 19 May 22/4: The zany Brewsters [in the play Arsenic & Old Lace] and their basement cemetery still get laughs – boffo laughs.
1957		Mad mag. Jan.–Feb. 15: Poohbah Trial Does Boffo B.O.
1963		G. Lambert Inside Daisy Clover (1966) 42: Boffo, that’s all I can say, it’s Boffo with me!
1981		J. Wambaugh Glitter Dome (1982) 154: A 25-million-dollar movie that was boffo in six openings.
1994		Eble Campus Sl. Apr. 2: boffo – interesting, good.
2000		Indep. Rev. 27 Mar. 4: The film is sure to be a big hit. Top boffo, as they say in Tinseltown.
2010		J. Ellroy Hilliker Curse 11: We were sweat-soaked from her boffo play with the defroster.
2015		J. Stahl OG Dad 176: Jessica Chastain moved relentlessly towards that [...] boffo ending.
2021		J. Ellroy Widespread Panic 223: ‘Your Rebel Without a Cause summary is boffo’.