adverb, adjective
- with the back of a horse, burro, etc., bare; without a saddle: to ride bareback; a bareback rider.
adjective, adverb
- (of horse-riding) without a saddle
- slang (of sex) without a condom
verb slang
- (intr) to practise unprotected sex
adj.
1560s, of riding, from bare (adj.) + back (n.).