'Chū hàn' literally means 'to emit sweat'—'chū' (out, to come out) combined with 'hàn' (sweat)—and functions as a verb meaning 'to sweat'. It describes the physiological process of sweat appearing on the skin, usually in response to heat, physical exertion, stress, or illness. Unlike English, which treats 'sweat' as both noun and verb, 'chū hàn' is almost exclusively verbal in modern usage; the noun 'sweat' is typically expressed as '汗水' (hàn shuǐ) or simply '汗'.

This verb commonly appears in everyday health-related contexts—discussing exercise, fever, nervousness, or weather effects—and is neutral in register, appropriate for spoken and written Chinese. It frequently occurs with aspect particles like '了' (le) or '在' (zài) to indicate completion or ongoing action, e.g., '他出汗了' (He started sweating) or '她正在出汗' (She is sweating). It does not take an object and is rarely used in formal medical writing, where terms like '多汗' (excessive sweating) may appear instead.