change up

Short definition from Wiktionary

Verb

1. 1
   To throw a pitch at a much slower than expected speed.
2. 2
   To confuse someone by doing something unexpected or in an unexpected way.
3. 3
   To vary.
4. 4
   To change to a higher gear in a vehicle.

Noun

1. 1
   A pitch thrown with the arm motion of a fastball, but which travels at a much slower velocity because it is released without the fingers adding power to the delivery.
2. 2
   An unexpected event.