Ratchet is a mechanical device that allows motion in only one direction. Picture a socket wrench: when you turn it clockwise to tighten a bolt, the ratchet mechanism inside lets it turn freely. But when you try to turn it counterclockwise, it locks and won't budge. This one-way design lets you keep your grip on the wrench and make repeated small turns without having to reset your hand each time.

The clever part is inside: a toothed wheel works with a small lever called a pawl that catches on the teeth. The pawl slides smoothly over the teeth in one direction but catches and prevents movement in the other direction, like trying to pet a cat backward against its fur.

You'll find ratchets in many tools and machines. Winches use ratchets so heavy loads don't slip backward. Some car jacks use ratchets so they can lift a vehicle gradually without dropping it. Even the winding mechanism in old-fashioned clocks uses a ratchet to keep the spring tight.

The word can also be used as a verb: when you ratchet up something, you increase it gradually, step by step, like how tension might ratchet up before a big game as the score gets closer.