A descriptive word ascribing to a shag of the highest echelon. It is an expression of post-coital delight of the equal of shagging a celebrity. It can also be interchanged for the word stupendous when used to describe other acts/objects
"That was fucktabulous darling, just like shagging Beyonce"
"What a fucktabulous bong, I am well and truly fucked"
"That was a fucktabulous film, I particularly liked the part where she smoked a cigar whilst inserting a wine bottle in her rectum"