This is a baseball term used in the rulebook to define the effort a player must make in order for a given rule to be called or not called. For example, the infield fly rule requires that a fielder could make the catch with, "ordinary effort." It is up to the umpire closest to the action to determine if ordinary effort applies. It also applies in the case of a wild pitch, in which case the official scorekeeper must determine if the catcher could have caught the ball with ordinary effort. One of the most common uses of ordinary effort is in determining if an error has occurred.
In the rules of Major League Baseball, the phrase ordinary effort is defined as, "a fielder of average skill at a position in that league or classification of leagues should exhibit on a play, with due consideration given to the condition of the field and weather conditions." This requires that the individual making the judgment call must take into account the average ability of a professional baseball player and the field and weather conditions. This can make it difficult for an umpire or scorekeeper to make the correct call every time. However, there are rules in places for specific cases where a statistic based on one of these call may be challenged.