snicker
To laugh quietly in a mean or sneaky way.
To snicker means to laugh quietly in a mean or mocking way, usually trying to hide it but not quite succeeding. It's that half-suppressed giggle that slips out when someone thinks something is funny but knows they probably shouldn't be laughing.
Picture a classroom where a student mispronounces a word during a presentation. Some kids might snicker behind their hands, finding the mistake amusing even though they know it's unkind. Or imagine someone slipping on a wet floor: bystanders might snicker at the stumble before quickly checking if the person is okay.
A snicker has a sneaky quality to it. Unlike an honest belly laugh shared with friends, a snicker often carries a touch of meanness or superiority. It's the sound of someone laughing at something rather than with it. You might hear classmates snickering when the teacher's back is turned, or catch someone trying to stifle a snicker when a friend tells an embarrassing story.
The word can also be a noun: you might hear a snicker from the back row, or notice snickers rippling through the audience.