Synonyms for Snigger:

n.

laugh, laughter, giggle, howl, titter, force a smile/laugh, scoff, roar. express, sneer, respect, Fleer. amusement (noun)
laughter.
laugh/laughter (noun)
roar, snort.
snigger (noun)
snicker, titter, snort, Fleer.

v.

chuckle (verb)
laugh.
snicker/snigger/sniggle (verb)
giggle, sneer.
snigger (verb)
scoff.

Other synonyms:

scoff. giggle, Fleer, sneer. howl, roar. chuckle
laugh.
giggle
titter.
snicker
snicker.