Source : Webster's Revised Unabridged Dictionary (1913)

Watchman \Watch"man\, n.; pl. {Watchmen}.
   1. One set to watch; a person who keeps guard; a guard; a
      sentinel.

   2. Specifically, one who guards a building, or the streets of
      a city, by night.

   {Watchman beetle} (Zo["o]l.), the European dor.

   {Watchman's clock}, a watchman's detector in which the
      apparatus for recording the times of visiting several
      stations is contained within a single clock.

   {Watchman's detector}, or {Watchman's time detector}, an
      apparatus for recording the time when a watchman visits a
      station on his rounds.

   {Watchman's rattle}, an instrument having at the end of a
      handle a revolving arm, which, by the action of a strong
      spring upon cogs, produces, when in motion, a loud, harsh,
      rattling sound.