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1.
Watching or listening to something that makes your balls hurt just from thinking about it
Paul - "yesterday I watched this video where some guy shoved a screwdriver up his penis!!"

Don - "dude, shut up, you're giving me a mental vasectomy"
by Ulysses H. Ficus January 31, 2011
11 5
 
2.
when you see something that is painful to a guys balls. and it hurts your mind.
did you see that guy get hit in the balls by an armadillo?" "yea.. i had a mental vasectomy
by Whale On A Boat February 12, 2011
1 1