(British)

To have sex (with). A vogue word of the late 1980s; first heard in the late 1970s and quickly picked up by the media as a useful, vigorous, but printable euphemism for fuck. (The word was first broadcast in a British TV comedy series; at a later date, the tennis champion Boris Becker was dubbed 'Bonking Boris' by the gutter press.) It is a childish synonym for 'hit'; the sexual sense may derive from the sound of energetic bouncing. Alter- natively, an extended correspondence in Private Eye magazine suggested that this had long been a schoolboy term meaning to masturbate or ejaculate. It may also be significant that the immediately prece- dent vogue word for copulate among teenagers was knob, which in backslang would give bonk.

'They do call it bonking after all, which, as everyone knows, is THE word used by promiscuous people who DON'T REALLY LIKE SEX.'

(Julie Burchill, Elle magazine, December 1987).