Say you're out for a walk with a friend when something falls from the sky: pigeon droppings. You're splattered, but your friend is untouched. This event is anything but funny to you, yet your friend can't stop laughing. Is this pigeon laughter?
Not quite, unless your friend is laughing in a very specific way. Pigeon laughter, which is often practiced in laughter therapy or laughter yoga, involves laughing without opening your mouth. By keeping your lips sealed, the laughter produces a humming sound, much like the noises a pigeon makes.
It's also been compared to the humming of bees, so if you're still angry at those darn pigeons for dropping poop on you, feel free to call it bees' laughter.