Very good, interesting, or smart. Said typically of things. This nifty little device helps you locate your keys if you can't remember where you put them.That's a nifty bike you've got there! Is it new?
nifty
1. mod. neat; smart. That is a pretty nifty car you have there.
2. n. a fifty-dollar bill. (From nifty-fifty.) He paid me with a nifty and a domino.