Hands down, one of the finest aspects of a woman's anatomy that can be enjoyed in any public venue.

Underboob is achieved by wearing a very short halter top or cropped tank, also known as an underboob shirt, which exposes the bottom areas of a woman's breasts.

Much like the combination of low-rise jeans and a thong, the underboob shirt can only successfully be worn by select few women.
In an ideal situation, a hottie will wear an underboob shirt to accessorize her low-rise jeans/thong combination. When this happens, all men in the vicinity will regard her as "hot" or "a sexy bitch", while their wives/girlfriend may refer to her as "trashy" or "a slutty bitch", but that's okay. Everyone knows she's a sexy bitch and they all want to do her.
by X. Phoratus February 21, 2005
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The awkward amount of breast protruding from beneath a bikini top. It is debatably sexy, but it is def a spring break must.
Wow, That girl on sweet 16 has the under boob thing going on..

Poor Nicole Ritchie, she doesn't have enough body fat to pull off the under boob.
by Sexy Lexi April 14, 2006
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Underboob: The only time in life when gravity is your friend.
"She's got underboob, so there's a small chance her boobs will slip out of her top, thanks to our good friend GRAVITY"
by flargenschmop March 27, 2010
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Generally, when a women wears a short cut top/pulls up their top to cover all but a portion of the bottom of the breast. Nipple can be shown, but often it is also covered.

Other ways to achieve underboob are: Handbra (covering the breast in the same way a short cut top would), or viewing from a low angle so that the point of view is looking up at the woman's breasts.
That woman's top gives her great underboob.
by JeffryGoldbloom October 06, 2016
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The under boob is very ellusive and rarely shows itself. To coax, said the under boob from hiding, one must adjust thine own bra to a point of maximum comfort. The constriction of the bra causes under boob to show underneath the restricted area pleasing those around, that in which interns to show gratitude shall rejoice in joyfull song and dance;giving it the title, "UNDER BOOB."
Tim: "Yo Sam, tuck that Under Boob away, you're giving me a boner!"

Sam: "Oh man, I apologize Tim, I constricted my bra to a maximum, and it just well, popped out!"
by Tayylaa January 10, 2011
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