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1.
The effect that occurs when a woman wears a bra that's a cup or two too small for her thus forcing her boobs to pillow above the edge of the cup creating deeper cleavage than normal.

A more elegant term for quad-boob.
That gal's bra is slightly too small. It's pushing her boobs up and giving her pillow top cleavage.
by TongueTiedGuy November 17, 2012