watch·tow·er (w?ch?tou??r)n. An observation tower on which a guard or lookout is stationed to keep watch, as for enemies, for forest fires, or over prisoners.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.watchtower (?w?t??ta??) n (Military) a tower on which a sentry keeps watchCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014watch?tow?er (?w?t??ta? ?r) n. a tower for a sentinel. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.watchtowerA tall tower for military observation, often part of a castle.Dictionary of Unfamiliar Words by Diagram Group Copyright © 2008 by Diagram Visual Information Limited