noun, noun or participle which takes 'suru', intransitive verb
involuntary laughter; laughing despite oneself
Laughing when one should not, or being unable to suppress laughter. Often used in situations where laughter is socially inappropriate.
厳粛な式典で失笑してしまった。
I burst out laughing at the solemn ceremony.
彼の真面目な顔を見て、思わず
Seeing his serious face, I couldn't help but laugh.
noun, noun or participle which takes 'suru', intransitive verb
scornful laughter; snicker
Colloquial use for laughing at someone or something with contempt or ridicule. Less common than the involuntary-laughter sense.
彼の失敗話に、皆が失笑した。
Everyone snickered at his story of failure.