taking my arse for a piss
Explosive, liquid diarrhea.
Example
Vince: "You've been in there for a while!"
Nelson: "Heavy night last night, just taking my arse for a piss!"
Vince: "I'll avoid trap two"
Vince: "You've been in there for a while!"
Nelson: "Heavy night last night, just taking my arse for a piss!"
Vince: "I'll avoid trap two"