A brand of expensive wrist watch. Actually spelled Hublot, but the YouBlow spelling is more accurate, due to the legend-in-their-own-mind type of person who wears them.
I saw that rich kid wearing a YouBlow watch at the nightclub last night. Watch a pompous douche.
just another way to say you suck. When people are annoying you or getting you mad or even if you had plans to do things with someone and all of a sudden they cant, you respond with "You Blow".