flat as a board

Flat as a board is the phrase used when describing how flat someone or something is, such as an object or other material item. It is a way of exaggerating the flat shape of any type of item. The cliche flat as a board is most commonly used for girls or women who are not well developed and their chest is flat, or for women whose stomachs are very flat (such as skinny women) and this term will be used.