ratchet

1. N-COUNT In a tool or machine, a ratchet is a wheel or bar with sloping teeth, which can move only in one direction, because a piece of metal stops the teeth from moving backward. (防倒转的)棘齿; 棘轮

The chair has a ratchet below it to adjust the height. 这把椅子下面有一个棘轮来调整高度。

2. V-T/V-I If a tool or machine ratchets or if you ratchet it, it makes a clicking noise as it operates, because it has a ratchet in it. 使(工具或机器)发出嗒嗒声; (工具或机器)发出嗒嗒声

The rod bent double, the reel shrieked and ratcheted. 该操作杆加倍弯曲，线轴发出刺耳的嗒嗒声。

She took up a sheet and ratcheted it into the typewriter. 她拿起一张纸，把它塞入打字机，发出一阵“嗒嗒”的声音。