叛变 (pàn biàn) is a verb meaning 'to defect' or 'to revolt'—typically referring to abandoning one's original allegiance, especially in political, military, or organizational contexts. The first character 叛 (pàn) means 'to betray' or 'to rebel', carrying strong connotations of disloyalty; the second character 变 (biàn) means 'to change' or 'to transform', emphasizing a decisive shift in loyalty or position. Together, they describe an active, often dramatic break from a group, cause, or authority.

This word is formal and serious, commonly used in historical accounts, news reports, or political discourse—not in casual speech. It implies intentionality and consequence, not just disagreement. While it can describe individual defection (e.g., a soldier switching sides), it may also refer to collective uprisings. Note that 叛变 is rarely used for personal, non-institutional changes (e.g., changing hobbies or opinions), where other verbs like 改变 (gǎi biàn) would be appropriate.