\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.