See the rule text (8)
(Fast Pitch) When the catcher fails to catch the third strike before the ball touches the ground and there are: 1. Fewer than two outs and first base is not occupied at the time of the pitch, or 2. Any time there are two outs.
A. When the third strike is: 1 Swung at and the pitched ball touches any part of the batter's person. 2 Not swung at, and the pitched ball hits the batter while the pitch is in the strike zone. 3 A pitched ball, in the umpire's judgment, which was prevented from entering the strike zone by any actions of the batter other than hitting the ball.
The batter-runner is out: A. (Fast Pitch) When the catcher drops the third strike and the batter-runner is put out prior to reaching first base. This is in effect if there are two outs or with less than two outs and first base is not occupied at the time of the pitch. B. After hitting a fair ball and the batter-runner is put out prior to reaching first base. C. After hitting a fly ball that is caught by a fielder before it touches the ground, any object or person other than a defensive player. Effect - Section 2A-C: The ball remains live.
O. (Fast Pitch) When a called or swinging third strike is caught by the catcher. P. (Fast Pitch) When the batter has three strikes and/or if there are fewer than two outs and first base is occupied at the time of the pitch. Q. Whenever the batter due up has left the game under the Short-Handed Rule.
When an infielder intentionally drops a fair fly ball, including a line drive or a bunt, which can be caught with ordinary effort with first, first and second, first and third or first, second and third bases occupied with fewer than two outs. Effect: 1. The ball is dead. 2. The batter-runner is out. 3. Runners must return to the base occupied at the time of the pitch. 4. If an infield fly is ruled, it has precedence over an intentionally dropped ball.
Normally, there are four areas which could constitute whether or not a batter swung at the pitched ball or checked their swing. A. Did the batter roll their wrists? B. Did the batter swing through the ball and bring back the bat, unless the batter draws the bat back before the pitch arrives? C. Was the bat out in front of the body? D. Did the batter make an attempt to hit the pitch? On a bunt attempt where the batter puts the bat across the plate and the pitched ball is out of the strike zone, a ball should be called unless the batter moves the bat toward the ball. In each of the above situations, the umpire should think in terms of priorities. First, was the pitch in the strike zone? If so, it is simply a strike. Second, did the batter swing at the pitched ball, or, in the case of a bunt attempt, did the batter move the bat toward the pitched ball? In either case, it is the plate umpire's call. If in doubt, or if blocked out, the umpire should call the pitch a ball. If the umpire calls the pitch a ball and the catcher requests the umpire to go for help, the plate umpire should ONLY ask for help if there is doubt in their mind as to whether or not the batter swung at the pitched ball. On a missed bunt attempt with two strikes, the dropped third strike rule applies. (Rule 8, Section 1B)
H. For each pitched ball swung at and missed which touches any part of the batter. I. If a pitched ball is swung at, missed, and then hit on the follow through. J. When any part of the batter's person or clothing is hit with a batted ball while the batter is in the batter's box and (FP) has fewer than two strikes. K. When a legally pitched ball hits the batter while the ball is in the strike zone. L. When a pitched ball is prevented from entering the strike zone by any actions of the batter other than hitting the ball. Effect - Section 4H-L: 1 The ball is dead. 2 A strike on the batter. 3 Each runner must return to the base occupied at the time of the pitch.
The ball cannot be intentionally dropped unless the fielder has actually caught it, and then drops it. Merely guiding the ball to the ground is not an intentionally dropped ball.