The Collaborative International Dictionary of English v.0.48:

Timekeeper \Time"keep`er\ (t[imac]m"k[=e]p`[~e]r), n.
   1. A clock, watch, or other chronometer; a timepiece.
      [1913 Webster]

   2. A person who keeps, marks, regulates, or determines the
      time. Specifically:
      [1913 Webster]
      (a) A person who keeps a record of the time spent by
          workmen at their work.
          [1913 Webster]
      (b) One who gives the time for the departure of
          conveyances.
          [1913 Webster]
      (c) One who marks the time in musical performances.
          [1913 Webster]
      (d) One appointed to mark and declare the time of
          participants in races or other contests.
          [1913 Webster]

WordNet (r) 3.0 (2006):

timekeeper
    n 1: (sports) an official who keeps track of the time elapsed
         [syn: timekeeper, timer]
    2: a clerk who keeps track of the hours worked by employees
    3: a measuring instrument or device for keeping time [syn:
       timepiece, timekeeper, horologe]