During the tennis match, his gaze darted between the ball and his opponent rapidly.

darted 是动词 dart 的过去式。dart 本意是"快速移动、猛冲"，常用来形容视线或小物体快速移动的动作，就像飞镖(dart)快速飞行一样。这里描述视线在球和对手之间快速来回移动。