knob polisher

A crude British slang term for a person who performs fellatio, used either literally or as a general-purpose insult implying someone is servile or sycophantic. Like many vulgar British insults, it's as often lobbed as a general term of mockery — meaning someone who does favours for others in a pathetically eager way — as it is used in its explicit literal sense. It fits into the British tradition of colourful, euphemism-based sexual insults that are rude but not entirely without humour.

(slang, vulgar) One who gives fellatio.