Wikipedia
In an automobile, ball joints are spherical bearings that connect the control arms to the steering knuckles. They are used on virtually every automobile made and work similarly to the ball-and-socket design of the human hip joint.
A ball joint consists of a bearing stud and socket enclosed in a casing; all these parts are made of steel. The bearing stud is tapered and threaded, and fits into a tapered hole in the steering knuckle. A protective encasing prevents dirt from getting into the joint assembly. Usually, this is a rubber-like boot that allows movement and expansion of lubricant. Motion-control ball joints tend to be retained with an internal spring, which helps to prevent vibration problems in the linkage.
The "offset" ball joint provides means of movement in systems where thermal expansion and contraction, shock, seismic motion, and torsional motions, and forces are present.
Usage examples of "ball joint".
That point, effectively a ball joint, did not want to move after so long, but Littlefeet was very strong.
Her rectangular head rotated mournfully around a single ball joint, and plate-sized eyes looked down at Teal.
Four or five body-lengths from the tower, a large pipe rose to twice his height, bent at a right angle, and ended in a ball joint straddled by a pair of massive bars rising to half the height of the tower.
The barrel was a stubby tube of cast steel with a 100mm bore, mounted on a ball joint in the center.
He found he had a tail on some sort of ball joint, a tail he could wag and even whip to an extent.
The entire hand turned backward on the wrist, as no human hand could do, as if it operated on a ball joint, and the pincers snapped at my fingers, forcing me to let go before he had a chance to cut me.
On the end is a squat foot, rubber tread on the bottom, swiveling on a ball joint.