shirtboob
When a girl has big boobs, but is wearing an unshapely t shirt. shirt boobs can often create the illusion that the girl is over-weight particularly if the shirt is too loose, but if she gets it right it's the hottest thing ever. the word is singular, because the illusion shirt-boob creates is that there is one big boob area
Wow look at that girls shirtboob. I wanna jiggle squeeze and suck those things so much arghh I just jizzed myself