be on the piss

be (out) on the piss

rude slang To go out and drink alcohol. Primarily heard in UK, Australia. My friends and I were out on the piss last night, so I hardly remember anything at all.
See also: on, piss
Farlex Dictionary of Idioms.

be on the ˈpiss

(British English, taboo, slang) be out at a pub, club, etc. and drinking a large amount of alcohol: I’m not sure if Jerry will be at work today — he was out on the piss with his mates last night.
See also: on, piss
Farlex Partner Idioms Dictionary
See also:
  • be (out) on the piss
  • piss up
  • piss-up
  • piece of piss
  • a piece of piss
  • take a piss
  • piss on (someone's) chips
  • piss on (someone's) bonfire
  • take the piss (out of) (someone or something)
  • take the piss out of