faint smile
彼はうっすらと薄笑いした。
He smirked faintly.
詐欺師は怪しい薄笑いを浮かべて近づいた。
The con artist approached with a suspicious faint smirk on his face.
取調官は容疑者の顔に浮かぶ薄笑いに強い違和感を覚えた。
The interrogator felt a strong unease at the faint smirk surfacing on the suspect's face.