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casus belli

[key-suh s bel-ahy, bel-ee; Latin kah-soo s bel-lee]
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noun, plural ca·sus bel·li [key-suh s bel-ahy, bel-ee; Latin kah-soos bel-lee] /ˈkeɪ səs ˈbɛl aɪ, ˈbɛl i; Latin ˈkɑ sus ˈbɛl li/.
  1. an event or political occurrence that brings about a declaration of war.

Origin of casus belli

1840–50; < New Latin: literally, occurrence of war
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for casus belli

casus belli

noun plural casus belli (ˈkɑːsʊs ˈbɛliː)
  1. an event or act used to justify a war
  2. the immediate cause of a quarrel

Word Origin

literally: occasion of war
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

Word Origin and History for casus belli

n.

1849, from Latin casus "case" (see case (n.1)) + belli, genitive of bellum "war" (see bellicose). An act justifying war.

Online Etymology Dictionary, © 2010 Douglas Harper