a bit on the side

a bit on the side

A person who is involved in a sexual relationship with someone who is married. Primarily heard in UK, Australia. I spotted Harry at the diner with a woman much younger than his wife. She must be his bit on the side.
See also: bit, on, side

a ˌbit on the ˈside

(slang) a sexual relationship with somebody who is not your regular partner: He’s always looking for a bit on the side.
See also: bit, on, side