- a wheel, with a grooved rim for carrying a line, that turns in a frame or block and serves to change the direction of or to transmit force, as when one end of the line is pulled to raise a weight at the other end: one of the simple machines.
- a combination of such wheels in a block, or of such wheels or blocks in a tackle, to increase the force applied.
- a wheel driven by or driving a belt or the like, used to deliver force to a machine, another belt, etc., at a certain speed and torque.
- a wheel with a grooved rim in which a rope, chain, or belt can run in order to change the direction or point of application of a force applied to the rope, etc
- a number of such wheels pivoted in parallel in a block, used to raise heavy loads
- a wheel with a flat, convex, or grooved rim mounted on a shaft and driven by or driving a belt passing around it
