A form of humor about being a douche -- often mistaken for actual douchery by people who don't know you very well. This is very similar to pretending to be a Bro in a humorous way. It is an attempt to be ironic by being more douchey than anyone who knows you would believe you were capable of.
NPH's entire character in How I Met Your Mother or in Harold and Kumar is a Douchegag.
or "Allow me to drop some knowledge on ya."
or "What were you saying? I couldn't hear you while you weren't cooking. Barefoot."