Uncaught third strike
In baseball and softball, an uncaught third strike (sometimes referred to as dropped third strike) occurs when the catcher fails to cleanly catch a pitch for the third strike. A pitch is considered uncaught if the ball touches the ground before being caught (a bouncing ball), or if the ball is dropped after being grasped (see also catch). In Major League Baseball, the specific rules concerning the uncaught third strike are addressed in Rules 6.05 and 6.09 of the Official Baseball Rules.
On an uncaught third strike with no runner on first base or with two outs, the batter immediately becomes a runner. The strike is called, but the umpire does not call the batter out. The umpire may also actively signal that there is "no catch" of the pitch. The batter may then attempt to reach first base and must be tagged or forced out. With two outs and the bases loaded, the catcher who fails to catch the third strike may, upon picking up the ball, step on home plate for a force-out or make a throw to any other fielder.
The purpose of the "no runner on first base or two outs" qualification is to prevent the catcher from deliberately dropping a third strike pitch and then initiating an unfair double or triple play with possible force plays at second base, third base, or home plate. The logic of the situation is similar to that which led to the infield fly rule.
Regardless of the outcome of an uncaught third strike, the pitcher is statistically credited with a strikeout. Because of the uncaught third strike rule, it is possible for a pitcher to register more than three strikeouts in an inning.
In Little League, in the Tee-Ball and Minor League divisions, the batter is out after the third strike regardless of whether the pitched ball is caught cleanly by the catcher. In Little League (or the Major Division), Junior, Senior, and Big League divisions, a batter may attempt to advance to first base on an uncaught third strike. Little League Major Division Softball and many other youth baseball leagues (such as the USSSA) also follow the rule.
Following a controversial play involving this rule in the ninth inning of Game 2 of the 2005 American League Championship Series, the application of the rule was changed when a comment was added in 2006 to Rule 6.09(b):
"Rule 6.09(b) Comment: A batter who does not realize his situation on a third strike not caught, and who is not in the process of running to first base, shall be declared out once he leaves the dirt circle surrounding home plate."
This comment represents the official interpretation of the application of the rule. Prior to this rule change, a batter was able to try for first at any time before entering the dugout.
On May 17, 2011, Miguel Cairo of the Cincinnati Reds advanced to first after leaving the dirt circle when the umpires failed to enforce Rule 6.09(b). 
- "Official Rules | MLB.com: Official info". Mlb.mlb.com. Retrieved 2011-09-28.
- "Los Angeles Angels vs. Chicago White Sox - Recap - October 12, 2005 - ESPN". Scores.espn.go.com. 2005-10-12. Retrieved 2011-09-28.
- Roder, Rick. Official Baseball Rules Changed for First Time in 10 Years. . Accessed 2007-03-14.
- "Confusion surrounds Cairo's strikeout in sixth | MLB.com: News". MLB.com. 2011-05-17. Retrieved 2011-09-28.