As an adjective. Someone who is so all around butt-fucking awesome that your mind gets high being around said person.
As a proper noun. Slang for Designated Driver.
As another noun. A company that produces "gangsta" and, or, "cool shit" for the general consumer.
DD, I just want to say I love you and if I were a fag, I'd do you on the spot, but I'm not, so your da man!
Ok, we're going on a drinking run so anyone gonna volunteer for being the DD?
Man, DD is da mos pimptastic shit a foo coul buy yo!