不倦 (bù juàn) is an adjective meaning 'untiring' or 'indefatigable' — describing someone who works, studies, or strives persistently without growing weary or losing enthusiasm. The character 不 means 'not', and 倦 means 'to become tired, weary, or bored'; together, they form a classical compound expressing unwavering diligence and sustained energy.

This word is commonly used in formal or literary contexts — especially to praise dedication in learning, teaching, caregiving, or craftsmanship. It often appears in set phrases like 孜孜不倦 (zīzī bù juàn, 'diligently and tirelessly') or in descriptive clauses before nouns (e.g., 不倦的探索者). While it carries positive moral weight, it is rarely used in casual speech and is more frequent in written Chinese, motivational writing, or biographical descriptions.