'Watchtower' definitions:

Definition of 'watchtower'

(from WordNet)
noun
An observation tower for a lookout to watch over prisoners or watch for fires or enemies

Definition of 'Watchtower'

From: GCIDE
  • Watchtower \Watch"tow`er\, n. A tower in which a sentinel is placed to watch for enemies, the approach of danger, or the like. [1913 Webster]