Suffix used at the end of many "gamer/nerdy" terms to emphasize the meaning of the word. Mainly used during competitive-online video games such as Halo 3 and World of Warcraft.
When a guy/ girl you like says "you are like my sister" or "you are like the little sister I've never had" or "I love you like a sis" It is worse than being friend zoned, it's all the way past friends to family. You probably have a 2% chance of getting out of the sister zone and having a relationship with that person.