The term used to describe a way of positioning your vehicle's windows so that they are 3/4 of the way rolled up. If the vehicle has rear windows, those windows should line up exactly with the front. This also accentuates the lines of the car and creates a smooth look while rollin through the hood. It is not uncommon to see this on a beater that has a purple flake paint job and twinkies but hasn't bothered to fix his A/C.
Gangsta 1 : Dat ride is hot, yo!
Gangsta 2 : Yeahh, and he's rollin in 3/4 stealth mode!
Gangsta 1 : Hot to death!
Gangsta 2 : I'd do that in my Dodge Neon, but my rear windows have cranks...
Gangsta 1 : You a fag dog!
To initiate "calvin mode" is to raise one's hands and place then flat on one's head in order to mimic an incredibly homosexual hairstyle. The hair in question is rumored to equate to the length of half a football field, and is reported to have pierced hot air balloons from the ground.
Calvin: "Were there dinosaurs before the earth was made?"
Mr. Ziprick: "Like they say on reality TV shows: Calvin, you are the biggest loser."
Group of Geniuses: "INITIATE CALVIN MODE!"