Top Definition
"Mu" is the correct answer to the classic trick question "Have you stopped beating your wife yet?". Assuming that you have no wife or you have never beaten your wife, the answer "yes" is wrong because it implies that you used to beat your wife and then stopped, but "no" is worse because it suggests that you have one and are still beating her. According to various Discordians and Douglas Hofstadter the correct answer is usually "mu", a Japanese word alleged to mean "Your question cannot be answered because it depends on incorrect assumptions".

Hackers tend to be sensitive to logical inadequacies in language, and many have adopted this suggestion with enthusiasm. The word "mu" is actually from Chinese, meaning "nothing"; it is used in mainstream Japanese in that sense, but native speakers do not recognise the Discordian question-denying use.

Thanks to Thrakem for the source of this definition.
A monk asked Joshu, "Does a dog have the Buddha nature?"
Joshu retorted, "Mu!"
by IKEA January 21, 2004
16 more definitions
a Greek letter used in physics to represent a frictional constant of a surface.
For this surface, mu k equals .3825

Beware of physics cows, they go "muuuuuuuuuuuuuuuuuuuuuuu..."

by Mike the Ekim December 24, 2005
A "Member Update" on any sort of forum or message board. They are usually weekly or bi-weekly, and they log the post gains of the members on a certain board. Top spammers spots are coveted.
The Elder Scrolls MU rawks so much!
by gtiff123 April 20, 2005
"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!"


A friend witnessing a man flirting with a woman.
Friend (aloud): "MU!!!"
by MNNGJ September 20, 2011
Abbreviated for the phrase, "Mobile Upload." Most commonly used on Facebook. Only those deeply affiliated with Mobile Uploads can use it. "Mupload" is the immature form of M.U.
That's such a cute m.u.! Let's upload it!
by musforeveR!!!! January 26, 2010
Mu is a letter in the Greek Alphabet. Equivilent to our "M".
Cows don't say mu.......
by Wickedax September 25, 2005
A little cute ball
Look at that nice mu! It's all round and cute!
by Kitkatmu June 10, 2011

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