flat chested Share definition Flag A woman/girl with very small or no breasts. Usually seen as a curse but some people like the lack of boobs. Jay: YO MAN that bitch be flat chested Carol: Damn that's so fucking hot flat chested by Kona-Chan March 31, 2016 0 0 Get merch Get the flat chested mug. Buy Now — $32.95 See more merch