The Collaborative International Dictionary of English v.0.48:

Timepiece \Time"piece`\, n.
   A clock, watch, or other instrument, to measure or show the
   progress of time; a chronometer.
   [1913 Webster]

WordNet (r) 3.0 (2006):

timepiece
    n 1: a measuring instrument or device for keeping time [syn:
         timepiece, timekeeper, horologe]

Moby Thesaurus II by Grady Ward, 1.0:

49 Moby Thesaurus words for "timepiece":
   Big Ben, alarm clock, alarm watch, astronomical clock,
   atomic clock, box chronometer, calendar clock, calendar watch,
   chronograph, chronometer, chronopher, chronoscope, clepsydra,
   clock, clock movement, clocks, clockworks, cuckoo clock, dial,
   digital clock, digital watch, electric clock, electronic clock,
   gnomon, grandfather clock, half-hour glass, half-minute glass,
   horologe, horologium, hourglass, hunter, independent-seconds watch,
   isochronon, journeyman, marine chronometer, metronome, repeater,
   sandglass, sundial, telltale, ticker, time switch, timekeeper,
   timepieces, timer, turnip, watch, watchworks, wristwatch