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act of war

noun
  1. an act of aggression by a country against another with which it is nominally at peace.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for act of war

act of war

noun
  1. an aggressive act, usually employing military force, which constitutes an immediate threat to peace
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012