A portmanteau of the words internet and etiquette that refers to any of many unwritten rules of conduct within an internet community that are generally, but not limited to being, no different than etiquette in the real world. Totally depends on the kind of community though as netiquette differs within communities for gaming, forum, YouTube, etc. Noun.
Player 1(Noob): "Ok guys, good luck and have a good game!"
Player 2: "I'm gonna make you my baby-back beezy Noob!"
Player 1(Noob): "Oh my gosh, that's so mean!"
Player 2: "Looks like someone's not used to Halo netiquette."
Mike: "Jack, I went all in and this fool just took out my pocket Aces with his pocket Kings and he says 'Sorry about that bro?'"
Jack: "Relax, that's just good poker netiquette."