A comment on the video breaks it down:
richhighnfly
I'm glad he let is be known that "dub" started in New York.. "Dub" is short for Double O which is a blood code that means no good, lame, hit, over, or etc it all depend on the context in which its being used.. But shoutout to Maco for keeping it 100.. "Dub" is definitely NEW YORK SLANG