snicker

snicker
/ˈsnɪkə(r); `snɪkɚ/ v
laugh in a suppressed, esp unpleasant, way; snigger 暗笑; 窃笑
    snickering at obscene pictures 看著春画偷偷地笑. =>Usage at giggle 用法见 giggle. snicker, n suppressed, esp unpleasant, laugh; snigger 暗笑; 窃笑.

牛津英汉双解词典