A cleft or fissure, especially in rock or earth; a split or opening.
From Old English clēofan meaning 'to split or cleave.' Related to modern English 'cleave,' the word evolved to describe natural geological formations and structural separations.
This Old English word is a linguistic cousin of 'cleave,' which is famous for being a 'contranym'—a word that means both something AND its opposite! Here it just means the splitting itself, a useful term for describing rocky terrain.
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