gaping bra

(Noun)
When a small-chested female wears a molded bra that is too big for her boobies, and the bra's gaping at the top. If you're into small breasts, this is a pretty good sign. The opposite is an overflowing bra.

"I'm an A but I usually wear B cups. A gaping bra improves my bust, gives the boys something to look at, and actually makes me feel sexier."