A shock is the uncomfortable feeling you get when an electric current passes through your body. If you stick your finger in an outlet, you'll get an unpleasant shock.
A shock can be a jarring surprise, like the shock of getting fired. If a human body goes into a state of shock, that person is near collapse, reeling from a traumatic situation. A shock of hair refers to a bushy mass of hair on a person's head. As a verb, shock can also mean "to inflict trauma on someone else," like shocking your mom with your news or you shock your dog's electric collar every time he tries to bite you.