ball-and-socket joint

US: (bôl′ən sok′it)

WordReference Random House Unabridged Dictionary of American English © 2025

ball′-and-sock′et joint′  (bôl′ən sok′it), 

1. Anatomy Also called enarthrosis. 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. Anatomy, Mechanical Engineering 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.

• 1660–70

Collins Concise English Dictionary © HarperCollins Publishers::

ball-and-socket joint, ball joint noun

1. a coupling between two rods, tubes, etc, that consists of a spherical part fitting into a spherical socket, allowing free movement within a specific conical volume