Nit
A nit is a very tight player who only plays premium hands and avoids risk. He folds most of his hands, and when he bets or raises, he usually has a strong hand.
The simple explanation
A nit waits for the best hands and folds the rest. You can beat a nit by stealing his blinds and folding when he shows strength. When he raises, give him credit for a strong hand.
A closer look
Nits are predictable, so they are easy to exploit. Raise their blinds often, since they fold too much, and avoid paying them off with marginal hands when they bet. A nit may be profitable at tight, low-stakes games but he loses value by missing profitable spots. The word is sometimes used as an insult, but a disciplined tight style is a strong foundation. The main fault is being too tight to make money from good hands.
A practical example
A player has folded for an hour and then raises under the gun. Everyone folds, because they know a nit has a premium hand.
Full explanation
A nit is a very tight player who only plays premium hands and avoids risk. He folds most of his hands, and when he bets or raises, he usually has a strong hand.
A nit is an extremely tight player who plays only the best hands.
His bets mean strength.
You can steal his blinds.
He is the opposite of a maniac.