[Fr., from pull, or from Low L. pullanus, a colt.] One of the mechanical powers, consisting of a wheel called the sheave, movable about an axis, and having a groove cut in its circumference, over which a cord or rope passes. The rope is attached at one end to a fixed point, and the force acting on the free end of the rope is doubled, but the load is only moved through half the space traversed by the rope. Pulleys are used either singly to change the direction of the power applied, or in various forms of combination to raise heavy weights.