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1 definition by MNNGJ

 
1.
MU
"MU" (Pronounced Moo) is short for Mentally Undressing.
It is when a person is flirting with a member of the opposite sex whilst staring at their physical form. A witness or a friend of the person flirting must then say aloud the word "MU".
Two friends witnessing a man flirting with a woman.
Friend 1: "That guy is totally MU-ing that woman"
Friend 2: "I know...MU!"

or

A friend witnessing a man flirting with a woman.
Friend (aloud): "MU!!!"
by MNNGJ September 20, 2011