detent
/dɪˈtent/noun
1- a catch in a machine which prevents motion until released（机器中的）止动器爪, 锁销。
1.1
- (in a clock) a catch that regulates striking（时钟中的）鸣钟报时控制器。
词源
late 17th cent. (denoting a catch in clocks and watches)： from French détente, from Old French destente, from destendre 'slacken'， from des- (expressing reversal) + Latin tendere 'to stretch'.