It still means
fuck off, but it’s a fuck off on steroids with its fists clenched, eyes staring and a snarl on its lips. But that’s not the end of it, you can be told to “ most definitely fuck right off”, where in addition to staring and snarling with its fists clenched sweating and trembling with anticipation for the tiny trigger that will let it rip your head off and shit down your neck. There are numerous other variations until you are told to “most
fucking definitely
fucking well fuck right fucking off”. If this sound incoherent it’s because it is; you are now faced with a berserk, ninja
vampire with titanium talons and diamond teeth who is a hairsbreadth away from howling chaos and the total destruction of you, your family and all your ancestors so that you become not even a memory.