1.NounA pitch thrown with added pressure by the index finger and a twisting wrist motion resulting in a motion to the right when thrown by a right-handed pitcher.
"The screwball is not thrown much because it tends to damage pitcher's arms."
2.NounOne who behaves in a crazy manner.
"I will not listen to this screwball any longer."
3.NounA screwball comedy.
4.AdjectiveCrazy, offbeat, bizarre, zany, or weird.