take the piss out of

take the piss (out of) (someone or something)

To tease, mock, or ridicule (someone or something); to joke or kid around (about someone or something). Primarily heard in UK, Ireland. If you are so serious that you can't take the piss out of yourself every once in a while, you're going to have a hard time enjoying most of life. It really hurt Steph's feelings to know that the group had been taking the piss out of her that whole time. Brian was a bit of a troublesome student and tended to take the piss whenever class began.
See also: piss, take
Farlex Dictionary of Idioms.

take the piss out of

Chiefly British
To tease or mock (someone).
See also: of, out, piss, take
American Heritage® Dictionary of the English Language, Fifth Edition.
See also:
  • take the piss
  • take the piss (out of) (someone or something)
  • take the piss out of someone
  • take the mick (out of someone or something)
  • take the mickey
  • take the mickey (out of someone or something)
  • take the mickey out of
  • take the mickey/mick
  • take the mike (out of someone or something)
  • take the Michael (out of someone or something)