The Collaborative International Dictionary of English v.0.48:

Chronometer \Chro*nom"e*ter\, n. [Gr. ? time + -meter: cf. F.
   chronom[`e]tre.]
   1. An instrument for measuring time; a timekeeper.
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   2. A portable timekeeper, with a heavy compensation balance,
      and usually beating half seconds; -- intended to keep time
      with great accuracy for use an astronomical observations,
      in determining longitude, etc.
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   3. (Mus.) A metronome.
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   Box chronometer. See under Box.

   Pocket chronometer, a chronometer in the form of a large
      watch.

   To rate a chronometer. See Rate, v. t.
      [1913 Webster] Chronometric