Either of the two rounded portions of the anatomy located on the posterior of the pelvic region, forming the lower part of the back and the upper part of the legs.

She slipped and landed on her buttocks.

The fleshy part of the human body that a person sits on.

He complained of soreness in his buttocks after the long bike ride.

Nautical: the after part of a vessel's hull where it broadens out on either side of the sternpost.

The ship’s buttock was reinforced to improve stability.