A pace that nobody can handle. A person can use riddium in any type of sports or task. It's simply a matter of complete domination.
GSP (with the french canadian accent): "aye'm gonna poot so much pressure on diz guy dat 'iz gonna fall, u kno. 'Iz not gonna be abel too 'andle mye riddum".
The english translation would be:
"I'm gonna put so much pressure on this guy that he's gonna fall, you know. He's not gonna be able to handle my rhythm."
Evidently, it's much cooler with the Quebec accent.
Rythm, as spoken in Georges St. Pierre's French Canadian accent. Refers to imposing his will on his opponents in the ring or octagon.
"No one can 'andle my riddum!" - Georges "Rush" St. Pierre, UFC Welterweight Champion