Tsurupeta (つるぺた)
It is a Japanese portmanteau word combining two onomatopoeias: tsurutsuru [つるつる], which means smooth, polished, especially hairless; and petan [ぺたん], which means flat, devoid of bumps and holes. So tsurupeta [つるぺた] describes a female body that’s flat above and smooth below. Via: tsurupeta