'扇耳光' is a verb meaning 'to slap (someone) across the face'. It combines three characters: 扇 (shān), which means 'to flap' or 'to strike with an open hand'; 耳 (ěr), meaning 'ear', used here metonymically to refer to the side of the face near the ear; and 光 (guāng), which in this compound functions as a suffix indicating completeness or force — literally 'bright', but idiomatically signaling a full, sharp, stinging impact. Together, the phrase evokes a loud, deliberate, often humiliating physical blow.

This expression is strongly associated with anger, punishment, or public shaming — not casual playfulness. It appears frequently in literature, film, and historical accounts to convey intense emotion or moral reprimand. While grammatically transitive, it usually implies intentionality and emotional weight, and may carry legal or ethical connotations depending on context.