1. Used to describe a young adult male so astoundingly self-centered, boorish and lacking in social graces that it must be the result of magic.
2. Much rarer, used to describe a young adult male who is astoundingly self-centered, boorish and lacking in social graces, who also happens to be a trained Magician.
A contraction of "douche" and "fantastic". Something displaying the qualities of a douche to an extreme or fantastic degree could be described as douchetastic.
"Elf", starring Will Farrel, is a douchetastic movie, because Will Farrel is a douche, and only other douches think he's funny.