When something is extending to the side or moving to the side, it’s lateral. "All of the lateral movement in tennis hurt her knees and she had to quit playing."
The adjective lateral comes from the Latin word lateralis, which means “belonging to the side” and the modern meaning is basically the same. In anatomy, views of the body from the left, as well as from the right are referred to as lateral. You can make a lateral career move, if the compensation and level of responsibility stay about the same (instead of moving up, you are moving to the side). A lateral pass in football is one that goes to the side or behind the passer, instead of directly towards the goal.