When a league of legends player (possibly pro) from the North American region uses the in-game flash summoner spell in a terrible and possibly game losing way, we define it as a NA flash. The term is often used by people from the Europe West region to make fun of the NA region and players, but unfortunately they are equally as bad and have not won Worlds in millennia.
Twitch Chatter 1: NA FLASH HAHA
Twitch Chatter 2: Nah but EUW