<p><strong>Noun</strong></p><ul><li>Nautical: A vertical blade at the stern of a vessel that can be turned horizontally to change the vessel's direction when in motion.</li><li>Aeronautics: A movable control surface attached to a vertical stabilizer, located at the rear of an airplane and used, along with the ailerons, to turn the airplane.</li><li>Any means of or device for governing, directing, or guiding a course, as a leader or principle.</li></ul>