Guapo in spanish means handsome. When applied in this sense it is used as a paradox to that definition however. Guapo is usually used by a group of friends as a nickname to the kid in the group who is the fattest and ugliest as a put down. It is basically a form of sarcasm.
Guapo means CRUNK. Like some one talkin shit.Some one who wants to fight or is acting bad.Some people use it as Elegant but if your using slang then it is Crunk.