Wiktionary
sniggeringly
adv. With sniggers; with sardonic laughter.
Usage examples of "sniggeringly".
Some boy in an “A” stream might have sniggeringly read out the naughty passages in Tony’s hearing.
But then, that was at least part of the reason why Gradgroat-Norchelites had been sniggeringly referred to as "Gradygroats" all those years.