"Fanto" means "fantastic," but with real enthusiasm; not the kind of "fantastic" you might say to just anyone, but to your real and true best friend when he/she does something extraordinary. It must always be shouted.
Friend: Hey, check out this pizza I bought for you. It is on a thin crust, and is topped with extra heapings of sausage, onion, and green pepper.
Short-hand for the word floccinaucinihilipilification, meaning the estimation of something as valueless (encountered mainly as an example of one of the longest words in the English language).