1 An old man with problems you don't want to know about.
2 My dad..... No names mentioned
3 A woman with serious problems who thinks she's a man.
4 Any one (male) who has problems or appears to have some kind of brain disorder
The weirdo man across the street picked up the paper from outside and stuck it in his pants.
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi