ball-and-socket joint

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun 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.
• noun A joint, as in a mechanical device, that permits rotary movement in all directions through the movement of a ball in a socket.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A joint in which one segment has a rounded end and the next segment has a bowl-shaped end, with the rounded end being fitted into the bowl shape, allowing the first segment to move around an indefinite number of axes which have one common center.