Rex Grossman is a pro quarterback currently part of the NFL's Washington Redskins team.

"Rax Grissman" is his /sp/ counterpart. This meme came into being on 4chan's newly-reborn /sp/ – sports board. Encyclopedia Dramatica states "Rax originated from one of /sp/'s cancerous Nod Flenders threads, but was made of win, and went on to become the subject of many epic threads and copypastas".

Rax Grissman essentially serves as /sp/'s mascot, signifying immense quantities of win and fail, lulz and trolling, all at once. This stems from Grossman's reputation as a talented, but highly inconsistent player. In 2006, he led his team at the time, the Chicago Bears, to the Super Bowl. His team lost and Grossman's play is seen as a major part of this. When the Bears needed a mere five yards or so to keep the ball and put themselves in a position to score late in the game, Grossman instead threw DEEP (read: UNLEASHED THE DRAGON) and the ball was intercepted, ending whatever chance the Bears had of staging a comeback to win the game.

Since then, Grissman is seen as something of a hero to /sp/'s denizens, a man raised to god-tier status despite (or perhaps because of) his enormous failures.

An example of Rax Grissman copypasta:

The NFC Championship

"It was 4th and goal on the one inch line with just seconds left in the NFC championship game. The Boars needed a touchdown to win so the coach called for a pitch to the running back for the game winner. Rax yelled, 'You know who I am? Im motherfucking Rax Grissman. You give me the fucking ball, faggot. This is my game.' Then in retaliation Rax broke both of the running back's knees, and knocked the backup unconscious. Coach had no choice and called far a fade route to the corner of the end zone, which Rax overthrew by a good 20 feet. The Boars had lost the game that day, but inside, Rax knew he was a winner."