Originated from hip hop websites and forums concerning rapper Jay-Z. It means someone that is obsessed with Jay-Z in one way or another to the point where they will either defend him at all costs (some even giving their lives) or incessantly talking about him with disgust and or hate, usually because Jay-Z didn't give them an autograph.
Yo you think Jay-Z is cool because he's rich? Nah man you a Jigga Warrior for real, GTFOH!