Green’s Dictionary of Slang

1. (US) used to express surprise or convey the impact of a sudden violent attack or blow.

1920		H. Wiley Wildcat 167: ‘Boy, roll ’em.’ ‘Wham! Seven. Shoots forty francs.’.
1920		T. Thursday ‘Shorter Hours, Longer Pay’ in Top-Notch 1 Sept. 🌐 ‘I’m going to show this tramp’ — pow! — ‘what a fair and square’ — wham! — ‘trouper does to birds who’ — zam! — ‘pull this kinda stuff!’.
1948		J. Archibald ‘Klump a la Carte’ Popular Det. July 🌐 I opened a box an whammo, it was a jack-in-the-box with a hunk of lead for a noggin.
1950		A. Buckeridge Jennings Goes To School 72: Wham! A beautiful corner kick.
1955		B. Schulberg On the Waterfront (1964) 59: All of a sudden something sets them off and whammo! it’s like snoozing on top of a volcano.
1961		R.A. Norton Through Beatnik Eyeballs 31: His fuse-box come down, shadow mine, then, wham, he’s on there.
1966		H.S. Thompson letter 28 Nov. in Proud Highway (1997) 589: So when somebody teed off on me, whammo!
1971		Wodehouse Much Obliged, Jeeves 170: They’re off their guard, and wham! you’ve got away with their umbrellas and cameras.
1976		Cab Calloway Of Minnie the Moocher and Me 111: Whammo, I had my first big hit.
1981		J. Ellroy Brown’s Requiem 105: I drink and I drink and I’m not drunk, and then wham, I’m out like a light.
1981		A.K. Shulman On the Stroll 22: They tell em what they want to hear, give em what they want to have, and then — whammo!
1985		(con. 1969–70) D. Bodey F.N.G. (1988) 171: I’ll wash my face with it every day from now on and whamo — Mr. Clean. Zit remover.
1992		R. Price Clockers 79: Another guy hopped out and passed around [...] crack bottles, wham wham wham, before [...] tearing off.
1993		(con. 1969) N.L. Russell Suicide Charlie 95: He had no desire to be in a war and, whammo, he gets called into the service.
1999		Guardian G2 12 July 7: WHAM! We are blasted with perfume.

2. attrib. use of sense 1, resounding, making an impact.

1952

W. Winchell On Broadway 18 Aug. [synd. col.] His wham click at the Capri is Main Stem gab.

3. expressing violence.

1998

(con. 1960s) G. Washington Blood Brothers 158: He took out his pistol and WHAMMO upside my head, scaring away the flies.