Top Definition
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
by rob1982 January 03, 2013
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