Calling Station
A calling station is a player who calls too much and rarely raises or folds.
The simple explanation
A calling station is a player who calls too much. He rarely raises and rarely folds, whatever his cards. He sees too many flops and calls bets with weak hands, so you can win a lot from him with good hands, but you cannot bluff him.
A closer look
The usual advice against a calling station is to bet your good hands for value and to bet them big, since he will call. Avoid bluffing and fancy plays because he will not fold. Calling stations are also loose passive players, and they are among the most profitable opponents at a table. A good player picks a seat to the left of one so that he acts after the station's mistakes.
A practical example
A player calls every bet with weak pairs. The table calls him a calling station.
Full explanation
A calling station is a player who calls too much and rarely raises or folds.
A calling station is a player who frequently calls bets instead of raising or folding, often regardless of his hand strength. The nickname suggests that he is a place where chips are always going to stop.
He tends to play passively and rarely starts the action. His mistakes are calling too often and not folding when he is beaten.
The way to beat him is to value bet your good hands and to avoid bluffing. His calls win money for you in the long run.
The term is often used in a derogatory way.