Pulley

n. wheel with a grooved rim around which a rope or cord is wrapped (when one end of the rope is pulled downward, the wheel spins and raises the opposite end)

A pulley (also called a sheave or block) is a wheel with a groove between two flanges around its circumference. The groove normally locates a rope, cable or  belt. Pulleys are used to change the direction of an applied force, transmit rotational motion, or realize a mechanical advantage in either a linear or rotational system of motion.
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Noun
1. a simple machine consisting of a wheel with a groove in which a rope can run to change the direction or point of application of a force applied to the rope
(synonym) pulley-block, block
(hypernym) machine, simple machine
(hyponym) bollock, bullock block
(part-holonym) block and tackle

(v. t.)
A wheel with a broad rim, or grooved rim, for transmitting power from, or imparting power to, the different parts of machinery, or for changing the direction of motion, by means of a belt, cord, rope, or chain.
  

(b. t.)
To raise or lift by means of a pulley.
  

pulley /'puli/
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