Pronunciation: (bôl'un sok'it), [key]
1. Also called enarthrosis. Anat., Zool.a joint in which the rounded end of one bone fits into a cuplike end of the other bone, allowing for relatively free rotary motion, as at the hip or shoulder.
2. Also called ball joint. a similar joint between rods, links, pipes, etc., consisting of a ball-like termination on one part held within a concave, spherical socket on the other.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.