갈퀴의 작용에 의해서 한쪽 방향으로만 회전을 전하고 반대 방향으로는 돌지 못하게 되어 있는 기어.
ratchet
noun [C] (DEVICE)
a part of a machine that allows movement in one direction only. It is usually a wheel with teeth-like parts that either slide over or lock against the free end of a bar:
The ratchet at the other end of the axle only turns one way.
Keep the ratchet mechanism lubricated with oil.
(also ratchet wrench)
a tool consisting of a metal handle and a socket, used for turning objects in one direction only:
The bolts can be removed with a ratchet.
I had almost every ratchet and wrench in the tool catalogue at my disposal.