I bow to your incomparable research skills, Quizmaster.
I'd love to see how our American cousins would do if every question about Baseball (or Basketball and NFL for that matter) were replaced with questions about Cricket, Rugby or Kabaddi lol.
It's a totally unconventional approach to the throwing a baseball. Every other pitch is intended to impart some spin on the ball to make it break, or curve, or sink, or even to simply arrive as fast as possible. The ideal knuckleball doesn't spin and it's speed is significantly slower.
A ball that's slower and doesn't spin sounds like it should be way easier to hit, but even the guys who have contracts in the hundreds of millions of dollars because of their prodigious batting abilities have serious trouble tracking the knuckleball as it comes to the plate. The fluid dynamics at play make the ball flit and move randomly from moment to moment. It's totally unpredictable... even for the pitcher.
If you get a chance, check it out on YouTube.