Green’s Dictionary of Slang

1. to hit (esp. on the head).

1945		R.L. Bellem ‘Coffin for a Coward’ in Hollywood Detective Dec. 🌐 She [...] started to bonk Bonham over the conk.
1965		J.P. Carstairs Concrete Kimono 172: I have been bonked on the head, dam’ near blown to glory in a wired car —.
1978		J. Webb Fields of Fire (1980) 170: If they move, bonk ’em one.
1999		Indep. on Sun. Rev. 5 Dec. 10: Larry bonks Moe on his noggin.
2001		(con. 1964–8) J. Ellroy Cold Six Thousand 648: Sirhan fell off horses. Sirhan bonked his head repeatedly.

2. to have sexual intercourse.

1986		P. Slabolepszy ‘Boo to the Moon’ in Mooi Street (1994) 115: Bonk a Wallaby! Intercourse with a horse, Nourse, [...] bonk a Wallaby!
1989		R.G. Barratt ‘Wellington’s On the Other Foot’ in What Do You Reckon (1997) [ebook] [of a woman] She [...] bonked me on the loungeroom floor.
1994		Penguin Bk of Aus. Jokes 332: He sprang the sailor bonking the girl.
1999		Guardian 12 July 18: Pictures of Princess Stephanie’s then husband bonking some model on a sun lounger.
2000		F. Mac Anna Cartoon City 118: Maybe they could be FWBs – Friends Who Bonk.
2002		S. Maloney Something Fishy (2006) 29: Princess Diana denies bonking rugger bugger.
2010		K. Richards Life 44: She caught him bonking an ARP warden in a blackout.
2023		(con. 1962) J. Ellroy Enchanters 27: [Elizabeth Taylor]’s bonking her costar.

3. (US campus) to break down, to wear out.

1997–2002		Hope College ‘Dict. of New Terms’ 🌐 bonk v. To fail or give up in a high profile, stressful situation. Typically used in the world of sports when an athlete does not perform well under pressure.
1999		‘Sl. Dict.’ http://slang.uoregon.edu 🌐 I bonked (Phrase) Source: Biker group. Meaning: One loses all energy to continue racing or riding. It happens when you lose glycogen stores. Context: Describing why one all of a sudden lost energy. Collected: 10/10/1999 .