1. doozy 
something that is difficult or daunting 
man that history exam was a doozy! i think i failed 
2.  doozy
Something extraordinary or bizarre. Etymology: perhaps alteration of daisy, and Duesenberg, a luxury car of the late 1920s and 1930s. It's an English expression.
"That footballer's form is a doozy!", 
"Man, that one was a real doozy!"
3.  Doozy
Something that is better than everything else. Also, a famous Runescape player who is one of the best in that game.
Man, I swear that weed was a doozy. ...