bachelor

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

• noun A man who has never been married.
• noun A person who has completed the undergraduate curriculum of a college or university and holds a bachelor's degree.
• noun A male animal that does not mate during the breeding season.
• noun A young knight in the service of another knight in feudal times.

from The Century Dictionary.

• noun Formerly, a person in the first or probationary stage of knighthood; a knight not powerful enough to display his banner in the field, and who therefore followed the banner of another; a knight of low rank. See knight bachelor, under knight.
• noun In universities and colleges: Before the fifteenth century, a young man in apprenticeship for the degree of master in one of the higher faculties, that is, of theology, law, or medicine. In modern use, a person who has taken the first degree (baccalaureate) in the liberal arts and sciences, or in divinity, law, medicine, etc., at a college or university: as, a bachelor of arts; a bachelor of science. See baccalaureate.
• noun A man of any age who has not been married.
• noun A woman who has not been married.
• noun In London livery companies, a person not yet admitted to the livery. A local name in the United States of a fish, Pomoxis annularis, of the Mississippi valley; a crappie.
• noun Sometimes incorrectly spelled batchelor.
• noun One of the young male furseals which are forced, through fear of the adult bulls, to herd by themselves at a distance from the breeding-grounds.

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

• noun A man of any age who has not been married.
• noun obsolete An unmarried woman.
• noun A person who has taken the first or lowest degree in the liberal arts, or in some branch of science, at a college or university.
• noun A knight who had no standard of his own, but fought under the standard of another in the field; often, a young knight.
• noun obsolete In the companies of London tradesmen, one not yet admitted to wear the livery; a junior member.
• noun (Zoöl.) A kind of bass, an edible fresh-water fish (Pomoxys annularis) of the southern United States.

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

• noun A man who is socially regarded as able to marry, but has not yet.
• noun The first or lowest academical degree conferred by universities and colleges; a bachelor's degree.
• noun Someone who has achieved a bachelor's degree.
• noun Canada An apartment consisting mainly of one large room which is the living, dining, and bedroom combined. A bachelor apartment.
• noun obsolete An unmarried woman.
• noun obsolete A knight who had no standard of his own, but fought under the standard of another in the field.
• noun obsolete Among London tradesmen, a junior member not yet admitted to wear the livery.
• noun A kind of bass, an edible freshwater fish (Pomoxys annularis) of the southern United States.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a knight of the lowest order; could display only a pennon
• noun a man who has never been married
• verb lead a bachelor's existence