The pools of sweat collected under large breasts. Usually under larger women's voluptuous bosoms. known to cause interesting sweat designs in t-shirts and can cause a number of problems.
bro did you check out the underboob sweat on that one over there?

yeah bro the design is kinda trippy!
by the utter definition June 12, 2014
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A term used for a bad smell in a classroom
"eww, it smells like Danny DeVito's underboob in here"
by Danny DeVito's underboob July 8, 2020
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The Underboob Pen Challenge is a trend that started in China in late January 2016. It has since then reached all corners of the Internet all around the world. The objective of the challenge is for a female to place a pen, or a similar object under her unsupported breast. It's supposed to prove weather that female is a 'real' woman or not.
Jill: Have you heard of the new "Underboob Pen Challenge?"
Sara: No, what's that?
Jill: It's yet another challenge that sets unrealistic beauty standards on women.
by Mymojodied January 28, 2016
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its where you fucking lay down on the side walk with your ass exposed on a really hot day and have your friends grandmother cook eggs on it and sell them at walmart, keeping them heated in an easy bake oven. It helps not to get shit on them or fart in the old women's face, because she could die from inhaling toxic gases.
Hey dude i just made $5 from making Underboob square lego eggs with sean's grandma!
dude your horrible.
by Rem yo October 4, 2010
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A term used by the Kubz Scouts when the gaming experience is getting intense.
I need to calm down, I have sweat on my underboob right now.
by kinno September 17, 2022
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