a joint, as that of the hip or shoulder, formed by a ball in a socket, allowing limited movement in any direction
See ball-and-socket joint in American Heritage Dictionary 4
A synovial joint, such as the shoulder or hip joint, in which a spherical knob or knoblike part of one bone fits into a cavity or socket of another, so that some degree of rotary motion is possible in every direction. Also called enarthrosis.
A joint, as in a mechanical device, that permits rotary movement in all directions through the movement of a ball in a socket. Also called ball joint.