Dictionary / Vocabulary / 豹変
ひょうへん
sudden change; complete change
Also written ひょう変
普段はとてもおとなしいナイスガイだが、理性のタガがはずれると人格が豹変する二重人格。
He's got a dual personality - usually a quiet "nice guy" type, but when he flips, his character changes.
君子は豹変する。
A wise man changes his mind, a fool never.