A deliberate misuse of the word "obviously" used with lashings of irony and/or sarcasm. Used in its purest form, it should sound to the other person as though you are agreeing with what they are saying but to anyone with half a brain the opposite is true. It is a perfectly acceptable response to someone who has just said something utterly stupid.
"Look, it wasn't my fault I wrote off the car. They should never have put a goddamn telegraph pole there in the first place!" "Odviously"