To ignore, fail to heed, or contradict a warning given to someone.
From Middle English dis- (prefix meaning 'opposite of' or 'not') combined with warn (from Old English warnian, meaning 'to caution'). The prefix dis- reverses or negates the action of warning.
This word captures a very human tendency—we often diswarn ourselves by ignoring advice we know is good. It's the opposite of heeding, which is why it's rarely used today; modern English just says 'ignore' instead, but this archaic form shows how productive the dis- prefix once was in Middle English.
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