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When someones mum wont let them do something, even though they are old enough to decide for themselves.

Overbearing, controlling mother.

Similar to being under your girlfriend/wifes thumb.(not cool)
"No way dude, Dave wants to get a tattoo and although he's 19, his mom wont let him"
"He's so under the Mum thumb!"
by nicko2 September 07, 2007

Words related to Mum thumb

mom thumb mums thumb thum thumb under the thumb