不惮 is a literary, formal verb meaning 'not to shrink from' or 'to be undaunted by'—it expresses resolute courage in the face of difficulty, danger, or hardship. The character 不 (bù) means 'not', and 惮 (dàn) means 'to fear' or 'to hesitate due to apprehension'; together, they form a compact, classical expression conveying steadfastness without timidity. It is rarely used in casual speech but appears frequently in essays, speeches, historical texts, and formal writing to highlight moral resolve or heroic determination.

This word often modifies verbs or follows subjects directly, typically preceding an action or challenge (e.g., 不惮艰险, 不惮牺牲). It carries a dignified, somewhat solemn tone and is commonly paired with abstract nouns like 艰险 (hardship), 牺牲 (sacrifice), or 批评 (criticism). While grammatically simple, its register makes it inappropriate for everyday conversation—it’s more at home in political rhetoric, biographical narratives, or inspirational discourse than in texting or small talk.