运动裤 (yùn dòng kù) literally means 'movement pants' — combining 运 (yùn, 'to move' or 'to transport'), 动 (dòng, 'to move' or 'motion'), and 裤 (kù, 'pants' or 'trousers'). Though the characters emphasize motion, the term specifically refers to soft, comfortable, elastic-waist pants designed for physical activity or casual wear — what English speakers call 'sweatpants'. They are commonly made of cotton, fleece, or polyester blends and feature relaxed fits, often with drawstrings and side pockets.

运动裤 is a neutral, everyday noun used across age groups. It appears in contexts like gym routines, home relaxation, school PE classes, or even as loungewear during travel or cold weather. Unlike formal trousers (西裤) or jeans (牛仔裤), 运动裤 prioritizes flexibility and breathability. While originally sport-oriented, modern usage includes fashion-forward versions worn outside athletic settings — though calling them 运动裤 still signals their functional origin.