To separate into parts; to break apart or undo the unity of something that was joined or unified.
From dis- (reverse/undo) + unify (to make one), created in the late 19th/early 20th century as a back-formation to express the opposite action of unifying.
This word is rarely used in modern English because 'divide' and 'separate' usually work fine—but 'disunify' specifically suggests breaking something that *was* unified, making it more precise for political or group contexts.
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