A person, thing, or organization at the forefront of anything online. Creating new concepts or applications that improve upon the internet in some way, or someone in said concept that is in the forefront of it.
1.Napster was an adventgarde person for being one of the first too create and help make music free online.
2.A person or group on a game like World of Warcraft that is innovative or at the top of their respective server or country.
3. Urban dictionary is an adventgarde organization for creating something for people too share their definitions online.