D defs.my
Entry 2 senses Webster, 1913

Buttock

/bŭt'-ək/ · But·tock · IPA /ˈbʌtək/
01 n. The part at the back of the hip, which, in man, forms one of the rounded protuberances on which he sits; the rump. Often used in the plura…
  1. 1.
    The part at the back of the hip, which, in man, forms one of the rounded protuberances on which he sits; the rump. Often used in the plural -- see buttocks. See: buttocks
  2. 2.
    The convexity of a ship behind, under the stern.(Naut.)
Syn. cheek.