have it off

British and Australian slang meaning to have sex with someone. Typically used in casual, informal conversation and carries a blunt, unpretentious connotation — it's the kind of phrasing found in tabloid headlines or bawdy pub conversation rather than anything romantic. The phrase is well-established in British English and has been in use since at least the mid-20th century. It can refer to a single encounter and often implies something opportunistic or casual rather than a committed relationship.