A simple combination of awesome and fantastic, with an o at the end to make it sound fancy-like. Usually used to make things sound a lot better and to convince others to agree with whatever you are trying to get out of them.
"Trust me, this joint will make you feel awesometastico!"
"Stealing cars is almost as awesometastico as sex!!"
When drunk, calling other drunk people awesometastico usually makes them wonder what the hell you are on and where they can get some, causing their attention to be on you.