What is the plastic part in front of vehicle that deflects air Is it a wind jam?

That plastic part in front of a vehicle that deflects air is called a bumper (although some bumpers incorporate other materials). While it *does* deflect air, "wind jam" isn't a standard automotive term. The term might be used colloquially, but it's not formally recognized. The bumper's air deflection is a secondary function; its primary function is to protect the vehicle in low-speed collisions.