Source : Webster's Revised Unabridged Dictionary (1913)

Detent \De*tent"\, n. [F. d['e]tente, fr. d['e]tendre to unbend,
   relax; pref. d['e]- (L. dis- or de) + tendre to stretch. See
   {Distend}.] (Mech.)
   That which locks or unlocks a movement; a catch, pawl, or
   dog; especially, in clockwork, the catch which locks and
   unlocks the wheelwork in striking.

Source : WordNet®

detent
     n : a hinged catch that fits into a notch of a ratchet to move a
         wheel forward or prevent it from moving backward [syn: {pawl},
          {click}, {dog}]