Green’s Dictionary of Slang

1. terrific, amazing, effective.

1971		L. Bangs in Psychotic Reactions (1988) 8: A group called the Leaves had a killer (that’s another word you ought to add to yer little yaksacks) hit with ‘Hey Joe.’.
1984		G. Tate ‘Stagolee Versus the Proper Negro’ in Flyboy in the Buttermilk (1992) 51: Prince the killer act in rock and roll.
1990		J. Wambaugh Golden Orange (1991) 148: I make killer omelets.
1999		Guardian Rev. 15 Oct. 16: What these Manchester sons have lacked is a killer album.
2000		Indep. 22 May 20: The minute hand on Big Ben is 11 feet long. Killer fact!
2004		E. Weiner Drop Dead, My Lovely (2005) 86: She batted her pea-green peepers at me and, with an actress’s killer smile, said, ‘So didn’t I do good?’.
2010		N. Bradley ‘Blind Old Kate’ 🌐 Our tomcat, Tibby, who’d [...] fix the poor old sardine with a killer stare.
2012		Izikhotane News (S. Afr.) 23 May 🌐 The Relecting Disaster Crew [...] specialises in dancing, killer punch lines, and girls.
2012		M. Lacher On the Bro’d 274: ‘[W]hat a killer time we’re gonna have’.

2. ghastly, terrible, demanding.

1987		(con. 1967) Bunch & Cole Reckoning for Kings (1989) 56: Killer submarine sandwiches with salami from some never-disclosed-nor-asked-about-animal.
1999		Observer 11 July 20: Nursing a killer hangover induced by too much pink champagne.
2006		C. Hiaasen Nature Girl 101: Gillian [...] complained of a killer hangover.

3. extreme, ultimate.

1988		R. Doyle Commitments 4: That was the killer argument, Outspan knew, altho’ he didn’t know what it meant.
1999		‘Master Pimp’ Pimp’s Rap 2: But this is the killer part, he had them fools conned so bad that they would get in debt for him.
2000		N. Barlay Crumple Zone 115: Not exactly a ragga dancehall queen’s batty riders ok, but short shorts, short killer shorts nevertheless, that she’s pulled like right to the crack.
2007		D.S. Mitchell Killer Tune (2008) 10: The killer tune is the song everyone’s playing.
2012		M. Lacher On the Bro’d 12: Derek’s awesomeness was just as sick and killer and off-the-chain, without any of the asshole shit.