I think you might be referring to the slang compliment. It is usually said to someone after they have done something of which the other person (speaking) highly approves. Often in response to some help received or a respected accomplishment.
It is often voiced: YOU DA' MAN! (I approve of that!, That's impressive!, I admire you!)
It is used somewhat similarly to YOU RULE!
Another use of "The Man" refers to a drug dealer, as in the Velvet Underground song "I'm Waiting for the Man", in which Lou Reed sings about going to Uptown Manhattan, specifically Lexington Avenue and 125th Street, to buy heroin.
"The Man" can also refer to the "establishment" (variably: the police, the government, big business, etc.). So, once again, the translation depends on the context.