[1] It is a shortening of the idiom taking the piss out of, which is an expression meaning to mock, tease, joke, ridicule, or scoff.
The term sometimes refers to a form of mockery in which the mocker exaggerates the other person's characteristics, pretending to take on their attitudes, etc., for the purpose of comedic effect at their expense.
The phrase is in common use throughout Britain and to a lesser extent Ireland, being employed by headline writers in broadsheet gazettes[3] and tabloids as well as colloquially.
[4][5] "Take the piss" may be a reference to the related (and dated) idiomatic expression piss-proud, which is a vulgar pun referring to the morning erection that a man may have when he awakens or may be caused by a full bladder pressing upon nerves that help affect an erection.
[6] As knowledge of the expression's metaphoric origin became lost on users, "taking the piss out of" came to be synonymous with disparagement or mockery itself, with less regard to the pride of the subject.