Makes someone annoyed, irritated, or angry; bothers or upsets someone.
From Middle English 'roilen,' possibly from Old French 'rouiller' meaning to muddy or disturb. Originally meant to stir up water (making it turbid), then evolved to mean disturbing someone's peace of mind.
The word literally comes from 'roiling' water—making it muddy and turbulent—so to rile someone is to 'muddy' their calm emotional state, which is a really vivid metaphor!
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