The phrase "The U" is refered to when one talks about The University of Miami. Although Miami doesnt have the letter U in it, that is not what the phrase intends. Miami is refered to as "The U" because it is the best University. Hence the name "The U" or very rarely, "The University".
Mike- "Dude, you got accepted to The U!"
Chris- "Yeah, i already bought tickets to the football games too."