snigger

1. V-I If someone sniggers, they laugh quietly in a disrespectful way, for example at something rude or unkind. 竊笑

Suddenly, three schoolkids sitting near me started sniggering. 突然，坐在我身邊的3個學童媮媮地笑了起來。

2. N-COUNT Snigger is also a noun. 竊笑

...trying to suppress a snigger. …極力按捺一陣竊笑。