
Snigger
Disrespectful Laughter
Use 'snigger' to describe a quiet laugh that can be rude or mocking. 
Subtle Mockery
'Snigger' often implies laughing at someone without them knowing, in an unkind way. 
Not Overtly Loud
'Snigger' means the laughter is quiet, possibly hidden, unlike a loud guffaw. 