To have a verbal contest over progressively worse mum jokes. It usually goes around full circle before someone gets mummed-out.
Kevin: Your mum's a slapper.
Joe: Your mum is a bigger slapper!
Kevin: Your mum invented being a slapper!
Joe: Your mum wrote the slapper's handbook!
Kevin: Your mum followed every move in the handbook!
Joe: Are you challenging me to a mum-off?
Kevin: Your mum likes a challenge... etc
Joe: Your mum is a bigger slapper!
Kevin: Your mum invented being a slapper!
Joe: Your mum wrote the slapper's handbook!
Kevin: Your mum followed every move in the handbook!
Joe: Are you challenging me to a mum-off?
Kevin: Your mum likes a challenge... etc
by rob1982 January 3, 2013

by Cos(Hamilton) November 14, 2022

by TheRunawayWagon March 24, 2019

by Jonsmum February 11, 2014

by George Longfield November 19, 2020

when someone has nothing to say to a sentence, they say the phrase "ur mum" or a "ur mum" joke since they cant think of anything else with their nincompoop brain.
"Ugh i wish you would listen to me, even my mom listens better" "probably because ur mums so fat and her ears are so big even when shes tired of your bullshit she still has to"
by the real fish comfirmed May 28, 2023
