This term is used in baseball to describe a couple different actions and scenarios. In regards to hitting, it refers to a hit which goes to the same side of the field as the batter is hitting from. Since baseball assigns positions from the view of the stands, an example of a pull would be if a right handed batter hit the ball into left field. Other uses of the term are closer to the English definition; a manager can pull a pitcher or hitter out of the game in order to put in a relief pitcher or pinch hitter, whichever the case may be.
When the term is used in baseball parlance, it often is in reference to a ball hit to the same side of the field as the batter hit it from. If a fan or sports broadcaster is discussing a substitution of a pitcher or batter, the use of pull is closer to its English definition. An example of its most common usage would be, "Billy really pulled that ball." In cases where pull is being used to describe a substitution, it may be used as such, "It looks like the Manager is going to pull Ace Pitcher out of the game."