Definition of tight
A tight player is a player who plays few hands preflop. The tight player will also be the one who makes big folds and bluffs very little. He will also be called a nit. The tight player will show up to the showdown with a very strong hand every time. The more players at the table, the fewer hands he will play. For example, a tight shorthanded player will play 15% of his UTG hands. If he is playing full ring, he may open between 8% and 12% of his hands.
How to play against a tight player?
Against a tight player, you respect his bets. If he bets and you have nothing, you fold. If he raises, unless you are very strong, you fold too. The way to make money against a tight player is to bluff him when he is out of position and has not shown any strength or has checked a few times. When playing against a tight player, you have to be prepared to make big folds. For example, if you 3bet JJ against a tight player and he 4bets you, chances are he has a hand like QQ, KK or AA!