1. Someone who's so afraid to lose a bet that they have to be coddled and convinced for an hour that they're going to have a great time and probably win, too. Eventually they may play, but by the time they get on the table the stakes are so low the table-time will eat any winnings you make.
2. someone who won't play unless they have a guaranteed sure win.
3. someone who'll squeeze a dollar 'til george's eyes pop out of the paper.
Typically, but not always, this player will only play solid starting hands, won't play early position without premium hands, doesn't defend the blinds, won't flat from the small blind in a multi-way pot without a decent hand, won't up the stakes in a home game etc. This person will tend to avoid gambling without an edge, whilst at the same time will take full advantage of any free drinks and/or food offered by a casino.
Kris: You are such a f**king nit.
In ancient times people used to ride asses, NITS.