# casus belli

> English word · Noun · IPA /ˈkeɪ.səs ˈbɛl.aɪ/

## Definitions
1. An act seen as justifying or causing a war; an act of war.

## Etymology
From Latin cāsus (“occasion”) + bellī (“for war”, literally “of war”).

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/casus-belli