Combination of douchebag and Dickhead. Instead of a douchebag, the person is also a dick.An insult used on someone not as often as douchebag but is more offensive and the right word when douchebag does not properly apply.
Person 1 : Dude i took the last beer in the fridge.
Person 2 : You douchebag Person 1 : if you think im a douchebag, wait till you see what Person 3 did.
Person 3 : I took a dump on your sink thinking it was a toilet and i am not cleaning it.
Person 2: YOU DICKBAG!!!!!
A Dickleback resides on Long Island and drives a giant pick up truck. He sometimes has an American flag or a Trump bumper sticker on there somewhere but is not a requirement. He cuts you off just to end up at the red light with you. When you pull over he is listening to the worst music the radio has to offer at a volume higher than normal ears can handle. He might have a half ass handlebar mustache or a style that should have been terminated for good circa 1986. You may also find a dickleback at a bar or music festival.