Green’s Dictionary of Slang

conked (out) adj.

also conked in, conking, konked out
[conk (out) v. (1)]

1. usu. of a machine or engine, broken, no longer working.

[UK] ‘I Want a G-Nôme’ in C.H. Ward-Jackson Airman’s Song Book (1945) 26: Give me the spluttering, conking G-nôme.
[UK]J. Buchan Mr Standfast (1930) 606: Archie passed back a slip of paper on which he had scribbled: ‘Engine conked. Must land at Micklegill. Very sorry.’.
[UK](con. WWI) Fraser & Gibbons Soldier and Sailor Words 138: Konked (Konked Out): An Air Force term used of an aeroplane engine stopped working [...] a general expression meaning ‘knocked out’, dead.
[US]S. Longstreet Decade 310: Too bad the giants are gone. Conked out, dead and buried, or selling shoe-laces.
[SA]H.C. Bosman Street-Women in Gray Theatre One 19: Your nerves is just conked in.

2. in ext. or fig. use, of a person, collapsed, asleep, dead.

[US]H. Ellison ‘With a Knife in her Hand’ in Deadly Streets (1983) 130: Is he conked?
[US]J. Kirkwood There Must Be a Pony! 70: The dogs were conked out in the trophy room.
[US]T. Wolfe Electric Kool-Aid Acid Test (1969) 84: One moment all conked out, but with her eyes open, staring.
[US](con. 1945) E. Thompson Tattoo (1977) 357: He [...] hurried to where Pete lay like a conked supplicant before a cross.
[US]S. King Dead Zone (1980) 101: The patient was completely conked out.
[UK]Scotland on Sunday mag. 7 Nov. 17: If I didn’t take heroin, I would be on the floor conked out with the skitters, shaking, being sick, hot and cold sweats.
[UK]K. Richards Life 403: Everyone else is conked out on the floor.