From the same daughter that gave us " dickhead", " dillhole". No idea as to the exact meaning, except that it's not good. " Dillhole" can be used in a teasing/affectionate way with someone you are close to. "Dickhead" by contrast, is only used in a pejorative, dismissive way about a third party, not in the room, who has proven untrustworthy and/or stubborn and difficult to deal with.
seth