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
Get the Mum-offmug. by TheRunawayWagon March 24, 2019
Get the Ur mummug. by mrs tosser August 3, 2025
Get the Nigel's dead mummug. by bangedurmumlastnight April 20, 2021
Get the ur mummug. S: "MA! I can't find the sharpie!"
M: "It's right there. You just left it on the shelf."
S: "Damn, you got some crazy mum vision."
M: "It's right there. You just left it on the shelf."
S: "Damn, you got some crazy mum vision."
by yogha September 17, 2023
Get the Mum Visionmug. 
