Definition of tight
A qualified 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 referred to as a nit. Player tight will show up for the kill with a very strong hand each time. The more players at the table, the fewer hands he will play. For example, a player tight in shorthanded will play 15% of his UTG hands. If he plays in the full ring, he may open between 8% and preflop% of his hands.
How do I play against a tight player?
When playing against a tight player, you have to respect his bets. If he bets and you have nothing, you fold. If he raises, unless he is very strong, you fold too. The way to make money against a tight player is to bluff him when he's out of position and hasn't shown any strength or has checked a few times. When playing against a tight player, you have to be ready to make big fold. For example, if you make a 3bet with JJ against a tight player and he bats you 4bet, chances are he has a hand like QQ, KK or AA!