Buttock

1. n. The convexity of a ship behind, under the stern.
2. n. The part at the back of the hip, which, in man, forms one of the rounded protuberances on which he sits; the rump.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.