ratchet

中文： 棘轮

1. A pawl, click, or detent for holding or propelling a ratchet wheel, or ratch, etc.
2. A mechanism composed of a ratchet wheel, or ratch and pawl.
3. A ratchet wrench.
4. A procedure or regulation that goes in one direction, usually up.
5. A mechanism for generating a new unique key for each message by moving forward in a sequence.
6. A noisemaker or musical instrument where sound is generated by a board striking against a rotating gear.

复数 ratchets