Nit

Insulting poker terms are similar to the game of poker itself, in so much as they are always evolving. Over the past few years, a poker fish became a poker donkey, and a rock changed to a nit. Are players even called nits any more?

Anyway, a 'poker nit' is basically a tight player who cannot play post-flop poker and relies heavily on playing strong pre-flop starting hands. They may be profitable players, but they are fearful of good players, to the point of folding the winning hand often to avoid being outplayed on later streets.