When a girl wears a bra that is one or more cup sizes too small to contain her breasts. The breasts are squeezed so that a small portion protrudes over the top of the bra, similar to the way the dough oozes from a Pillsbury can after the seal has been popped.
Candy: "Shoot, I must have grabbed my roommate's bra by mistake this morning!"

Brenda: "Right?! You've got some serious Poppin' Fresh Boob going on over there!"
by That Chick from Accounting February 16, 2011
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