noun, noun or participle which takes 'suru'
faint smile; slight smile
A subtle, often involuntary or ambiguous smile. Can imply a hint of amusement, embarrassment, or a knowing look. Compare with 薄笑い, which is similar but may be slightly more common.
See also: 薄笑い
彼は薄ら笑いを浮かべながら、何も言わなかった。
He wore a faint smile and said nothing.
その話を聞いて、彼女は薄ら笑いした。
Hearing that story, she gave a slight smile.