'Watcher' definitions:

Definition of 'watcher'

From: WordNet
noun
A close observer; someone who looks at something (such as an exhibition of some kind); "the spectators applauded the performance"; "television viewers"; "sky watchers discovered a new star" [syn: spectator, witness, viewer, watcher, looker]
noun
A guard who keeps watch [syn: watchman, watcher, security guard]
noun
A person who keeps a devotional vigil by a sick bed or by a dead body

Definition of 'Watcher'

From: GCIDE
  • Watcher \Watch"er\ (-[~e]r), n. One who watches; one who sits up or continues; a diligent observer; specifically, one who attends upon the sick during the night. [1913 Webster]

Synonyms of 'watcher'

From: Moby Thesaurus