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The sudden, often irresistible urge to do something incredibly stupid.
Because third nipples are so weird and unnatural, they cause people who have them to do weird and unnatural things.
A good excuse for doing something weird if you do have a third nipple.
"Jonny, WHY did you stick your foot in that glass jar?"
"Third nipple impulse! I couldn't help it!"
"Why did you walk around with it like that?!"
by Mrs. Horrible November 23, 2008
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