1: the 'cool' way of laughing. The way Peter Griffin laughs in Family Guy.

2: Something Hootowls say. They say this because once, in a concert while performing "Alligator Sky", at the end of the song, Adam (if you do not know who this is, you obviously didn't click on Hootowl ) made an inhuman (adorable) noise that is believed to be spelled "Nyahaha".

Laughing like a Japanese cat person also known as a "Neko"

Neko's are seen in Japanese Anime