卖力 (mài lì) literally combines 卖 (mài, 'to sell') and 力 (lì, 'strength' or 'effort'), but its meaning is idiomatic: it describes putting forth vigorous, wholehearted effort — as if 'selling one’s strength' to show full commitment. It emphasizes visible, energetic exertion rather than quiet diligence.

This word is commonly used in spoken and informal written Chinese to describe enthusiastic participation or hard work, especially in physical, performative, or team-oriented contexts — like sports, performances, group projects, or manual labor. It often carries a slightly positive or admiring tone, implying commendable dedication, though occasionally hints at overexertion if context suggests exhaustion. Unlike more neutral terms like 努力 (nǔlì), 卖力 stresses outward intensity and observable effort.