(adjective)
having a concussive effect, causing some physical sensation or impact such as vibration or a shock/jolt;
e.g. The car made a jarring impact with the truck, causing everyone to be thrown forward in their seats.
(verb)
having a disturbing or unpleasant effect on something, or to somehow be strikingly or shockingly conflicting with something;
e.g. The sound of his voice was jarring on my nerves and making my head ache.
(verb)
sending a strong and damaging or painful shock through something or someone, especially causing an unpleasant jolt or vibration as a result of a strong strike or impact;
e.g. The car was jarring me every time it started moving again.