coquettish smile; flirtatious smile
A smile intended to charm or attract someone, often with a nuance of calculated seduction. The kanji 媚 carries a connotation of obsequiousness or flattery.
She gave him a coquettish smile.
その女優はカメラに向かって媚笑を浮かべた。
The actress flashed a flirtatious smile at the camera.
Compound of 媚 (bi, 'flattery, obsequiousness') and 笑 (shō, 'smile, laughter'). The exact historical derivation is uncertain, but the word is used in modern Japanese to describe a calculated, alluring smile.