detent
Concise Oxford English Dictionary © 2008 Oxford University Press:
detent /dɪˈtɛnt/
▶noun a catch in a machine which prevents motion until released.
■ (in a clock) a catch that regulates striking.
– origin C17: from Fr. détente, from OFr. destente, from destendre ‘slacken’.
'detent' also found in these Oxford entries:

