'Buttock' definitions:

Definition of 'buttock'

From: WordNet
noun
Either of the two large fleshy masses of muscular tissue that form the human rump [syn: buttock, cheek]

Definition of 'Buttock'

From: GCIDE
  • Buttock \But"tock\, n. [From Butt an end.]
  • 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.
  • Syn: cheek. [1913 Webster]
  • 2. (Naut.) The convexity of a ship behind, under the stern. --Mar. Dict. [1913 Webster]