Source : Webster's Revised Unabridged Dictionary (1913)

Timer \Tim"er\, n. (Internal-combustion Engines)
   In electric ignition, an adjustable device for automatically
   timing the spark.

Timer \Tim"er\, n.
   A timekeeper; especially, a watch by which small intervals of
   time can be measured; a kind of stop watch. It is used for
   timing the speed of horses, machinery, etc.

Source : WordNet®

timer
     n 1: a timepiece that measures a time interval and signals its
          end
     2: (sports) an official who keeps track of the time elapsed
        [syn: {timekeeper}]
     3: a regulator that activates or deactivates a mechanism at set
        times