It pretty much means to have a massive spazz attack. Like if you're really craving some cigarettes and your friend won't give you any, and you go all pissy on their ass and then soon, people will be saying, "They was being a complete dick today."
Chris: Give me a fuckin' cig man.
Tony: Nah, this is my last one dickface.
Chris will Flip-A-Tit. And pretty much beats Tony's ass to the floor.