Laughter, Susannah would later reflect, is like a hurricane: once it reaches a certain point, it becomes self-feeding, self-supporting. You laugh not because the jokes are funny but because your own condition is funny. ↗
He sniggered.
He didn't like to think of himself as the sort of person who giggled or sniggered, but he had to admit that he had been giggling and sniggering almost continuously for well over half an hour now. ↗