When you need the toilet and you do both.. at the same time!

Another definition is a random phrase circulating my school- "Poo and wee- willy and bum"

A pharse used in Christchurch, New Zealand as a greeting or general statement. Commonly yelled in a high pitch tone. Can have variants of different use of tone and pace.

Kids ask what's for tea so I tell them poo and wee for tea