A sarcastic way of saying bullshit, as in saying "bullshit, fantastic!" Usually used alone as an exclamation after the occurrence of a negative or disagreeable event.
*after Tigers lose in 6th inning due to rain with go ahead run at the plate*
"That's bullshitastic dude"
*teenagers in a shitty car in a liquor store parking lot*
Adam: Dude Carl won't sell me any 40s.
Bob: What? He's your brother dude he knows we ain't gonna get caught.
Adam: He says they know.
Bob: That's bullshitastic! Now what?