tit spillage 

When a girl with large breasts wears a small bra, thus her tits spill over the top of her bra. also known as muffin top of the breasts.

"Dude, Jess has some major tit spillage goin on"
"woaaaahhhhh..."

tit spillage by ta boob expert July 8, 2009

Tit spillage 

The section/area of a womans tit, that protrudes past the cup of her bra, which indicates that the tit has literally spilled from the bra cup as it is to large for the bra.

It's the bra equivalent of a muffin top

Man 1 Woah look at the tit spillage on her
Man 2 OMG those tits are way to big for that bra

Tit spillage by Heloby October 26, 2012