Green’s Dictionary of Slang

boffo adj.

[fig. use of boff v. (1) + -o sfx (7)]

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

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