Mersey steamer

Northern English term originating in Liverpool. A very large and noxious shit.

Scouser 1 (just vacating a toilet): "Keep out of there mate."
Scouser 2: "Why, mate?"
Scouser 3 (wafting his hand): "I've just berthed a Mersey steamer!"

by Wizards Sleeve February 14, 2007