captain

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun One who commands, leads, or guides others, especially.
• noun The officer in command of a ship, aircraft, or spacecraft.
• noun A precinct commander in a police or fire department, usually ranking above a lieutenant and below a chief.
• noun The designated leader of a team or crew in sports.
• noun A commissioned rank in the US Army, Air Force, or Marine Corps that is above first lieutenant and below major.
• noun A commissioned rank in the US Navy or Coast Guard that is above commander and below commodore.
• noun One who holds the rank of captain.
• noun A figure in the forefront; a leader.
• noun One who supervises or directs the work of others, especially.
• noun A district official for a political party.
• noun A restaurant employee who is in charge of the waiters and usually attends to table seating.
• noun A bell captain.
• transitive verb To act as captain of; command or direct.

from The Century Dictionary.

• To act as leader to; be captain over; command.
• noun In archery: The winner of a captaincy at a shooting-match.
• noun A competitor at a shooting-match or public meeting assigned to a particular target to score for the other archers and to keep order.
• noun One who is at the head of or has authority over others; a chief; a leader; a commander, especially in military affairs.
• noun More specifically
• noun In the army, the officer who commands a company, whether of infantry, cavalry, or artillery.
• noun In the navy, an officer next in rank above a commander, and ranking in the United States service with a colonel, and in the British with a lieutenant-colonel, and after three years' service with a colonel, in the army. Officers of this grade in the British service were formerly designated post-captains.
• noun The commander or master of a merchant vessel.
• noun In some of the public schools of England, a title given to the senior scholar.
• noun In base-ball, rowing, etc., the head or leader of the nine, the crew, or the body of players on one side.
• noun In mining, the head man or superintendent of the mining operations; the person who directs and is responsible for the miners' work. As a title, often abbreviated capt.
• noun A name commonly given, in the form long-finned captain, to the fish otherwise known as the lanthorn gurnard.
• [The orig. (ML.) use, but in E. later than the noun use.] Of chief rank, excellence, or value; chief; principal.
• Of commanding character; fitted to lead.

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb rare To act as captain of; to lead.
• noun A head, or chief officer.
• noun The military officer who commands a company, troop, or battery, or who has the rank entitling him to do so though he may be employed on other service.
• noun An officer in the United States navy, next above a commander and below a commodore, and ranking with a colonel in the army.
• noun By courtesy, an officer actually commanding a vessel, although not having the rank of captain.
• noun The master or commanding officer of a merchant vessel.
• noun One in charge of a portion of a ship's company
• noun The foreman of a body of workmen.
• noun A person having authority over others acting in concert.
• noun A military leader; a warrior.
• noun The Spanish governor of Cuba and its dependent islands.
• noun a lieutenant with the rank and duties of captain but with a lieutenant's pay, -- as in the first company of an English regiment.
• adjective rare Chief; superior.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A chief or leader.
• noun The person lawfully in command of a ship or other vessel.
• noun An army officer with a rank between the most senior grade of lieutenant and major.
• noun A naval officer with a rank between commander and commodore.
• noun A commissioned officer in the United States Navy, Coast Guard, NOAA Corps, or PHS Corps of a grade superior to a commander and junior to a rear admiral (lower half). A captain is equal in grade or rank to an Army, Marine Corps, or Air Force colonel.
• noun One of the athletes on a sports team who designated to make decisions, and is allowed to speak for his team with a referee or official.
• noun The leader of a group of workers.
• noun A maître d'.
• noun southern US An honorific title given to a prominent person. See colonel.