Shortened version of fabulous for those that are snooty and think their sh*t don't stink. It describes something that is really great, and well...fabulous!
(1) Did you see that new Armani sports coat. The design is fabu! (2) Your girlfriend is cool with you straying a bit? She is so fabu!
A person of sheer perfection and fabulousness. Usually named Ryan, these "fabu" people are just so amazingly awesome that no other words can describe them. In rare occasions, some fabu people are named Lee-Anne...very rare occasions...