1. Anat.a flexible joint.
2. an artificial appendage, limb, or the like, esp. one activated and controlled by a computer, as the mechanical arm of a robot.
3. a device by which two or more sections of a vehicle are linked together so as to allow greater capacity, flexibility of movement, etc.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.