Be on the piss
Definition 1 of 1
Pro Tip 1/3Informal Slang
Used casually among friends, not in professional or polite company. 
They planned to be on the piss this Saturday.
Pro Tip 2/3Potentially Negative
Sometimes implies irresponsible behavior or excessive drinking. 
He missed work because he was on the piss again.
Pro Tip 3/3Country Specific
Commonly used in the UK and similar cultures; might be misunderstood elsewhere. 
Visitors were confused when locals talked about being on the piss.