From Wiktionary, the free dictionary
Literally, “to have an erection like a bull”.
- IPA(key): /bɑ̃.de kɔ.m‿œ̃ tɔ.ʁo/, /bɑ̃.de kɔ.m‿œ̃ to.ʁo/
bander comme un taureau
- (of a man, simile, vulgar, sexuality) to have a strong boner (to be very aroused and have a strong erection)