When you lose weight, and your boobs shrink, but you are to cheap to buy new bras so there is a gap. The extra space is filled with the ghost of your former boob.
Boyfriend (touches boob)- What? There's nothing in there.

Girl- Yeah, I know, the bra is too big. It's just my phantom boob now.
by LemonZest June 20, 2016
Get the Phantom Boob mug.