Godan verb with 'u' ending, Intransitive verb
to laugh
クラスのもの皆が彼の冗談に笑った。The whole class laughed at his joke. to smile
Godan verb with 'u' ending, Transitive verb
to sneer; to ridicule
esp. 嗤う
Godan verb with 'u' ending, Intransitive verb
to be dumbfounded; to be flabbergasted
as 笑ってしまう or 笑っちゃう
Also written 嗤う【わらう】