a wheel used to transmit power or motion by means of a belt, rope, or chain
a wheel with a grooved rim that is used with a rope or chain to change the direction and point of application of a pulling force
one or more such wheels together with a block holding it or them
a wheel used to transmit power or motion by means of a belt, rope, or chain passing over its rim
[Middle English pouley from early French poulie, prob ultimately from Greek polos axis, pole]