'Jaaaaaaaag' is a slang word, primarily used by Jeremy Clarkson that is short for Jaguar. It was first used in the 13th series of Top Gear. Used in context, "Jaaaaaaaag" refers to a Jaguar-owner who is sleazy or old (e.g. "Do you want to come for a ride in my jaaaaaaag?") as it is the presenters opinionate that someone with these characteristics would drive a Jaguar.
As expressed in the section "Are you a Jaaaaaaaag Driver?" of The Big Book of Top Gear 2011, a Jaaaaaaaag driver is someone who is a scammer, can't pay the bills, a thief, and a flirter. Richard Hammond gave another example of the word Jaaaaaaaag in context during the 13th series by saying "I'm terribly sorry but I ran over your dog... in my Jaaaaaaaag".