The pitcher overthrew the ball, and the outfielder couldn't catch it.

overthrew 是动词 overthrow 的过去式。overthrow 由前缀 over-（表示"超过、过度"）和动词 throw（投掷）组成，字面意思是"投掷过度"，在这里指"投球过高"或"投球过猛"。