腐朽 (fǔxiǔ) is an adjective meaning 'decadent' or 'decrepit', describing something that has deteriorated morally, physically, or structurally—often implying deep-rooted decay beyond simple aging. The character 腐 means 'rotten' or 'putrid', evoking organic decomposition; 朽 means 'decayed' or 'worn out', especially referring to wood or other natural materials that crumble with time. Together, they intensify the sense of irreversible, advanced deterioration—not just old, but morally bankrupt or physically collapsed.

This word carries strong negative connotations and is commonly used in formal, literary, or critical contexts: describing outdated ideologies, corrupt institutions, crumbling buildings, or morally bankrupt individuals. It appears frequently in political discourse, historical analysis, and classical literature, where it evokes both physical ruin and ethical collapse. While it can describe literal decay (e.g., rotting wood), its most frequent modern use is metaphorical—especially for social or systemic decline.