Came together in a loud, harsh collision of sound; or fought/disagreed intensely with someone.
From imitative/onomatopoetic origins—'clash' sounds like what it means! The word appeared in Middle English and describes both physical collisions and conflicts between people or ideas.
The word 'clash' is onomatopoeia—if you say it out loud, your mouth makes a sharp 'sh' sound like two swords hitting! That's why it perfectly describes both the sound of metal striking and the harsh feeling of two opposing forces meeting.
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