A whip is a cord or piece of leather used for hitting an animal or a person, and to whip something or someone is to strike them with a whip. You can also figuratively whip an opponent or whip someone in shape. Giddy up!
When you hit an animal with a whip, you whip it. Some animal rights activists object to horse racers using whips. You can also use this verb to mean "defeat by a lot," like when your basketball team whips the opposing team. A chef whips cream by whisking or mixing it until it's airy and frothy. If your teacher says he's going to "crack the whip," he means he's planning to use his authority to make the class work harder. And, fittingly, a political whip is someone who enforces discipline among party members.