cadet

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

• noun A student at a military school or in a military program training to be an officer.
• noun A student training to be a police officer.
• noun A younger son or brother.
• noun A youngest son.

from The Century Dictionary.

• noun The younger or youngest son.
• noun Hence One of the younger members, or the youngest member, of any organized association or institution.
• noun One who carried arms in a regiment as a private, but solely with a view to acquiring military skill preparatory to a commission. His service was voluntary, but he received pay, and was thus distinguished from a volunteer.
• noun A young man in training for the rank of an officer in the army or navy, or in a military school.
• noun An East Indian bird, Æthopyga miles, a species of fire honey-sucker, of the family Nectariniidæ.
• noun A young man who, for the sake of the practical experience to be gained, works with the men on a sheep- or cattle-farm without pay.
• noun A student in engineering or any of the applied sciences who, in completion of his course (or earlier), seeks practical experience by entering the service of some large establishment where the principles be has been studying are applied, and works there for little or no pay.
• noun One who prostitutes a woman and lives on her earnings as a prostitute while cohabiting with her; also, one who seduces young women and sells them to houses of prostitution.

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

• noun The younger of two brothers; a younger brother or son; the youngest son.
• noun A gentleman who carries arms in a regiment, as a volunteer, with a view of acquiring military skill and obtaining a commission.
• noun A young man in training for military or naval service; esp. a pupil in a military or naval school, as at West Point, Annapolis, or Woolwich.
• noun In New Zealand, a young gentleman learning sheep farming at a station; also, any young man attached to a sheep station.
• noun Slang, U. S. A young man who makes a business of ruining girls to put them in brothels.

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

• noun A student at a military school who is training to be an officer.
• noun A younger or youngest son, who would not inherit as a firstborn son would.
• noun in compounds Junior. (See also the heraldic term cadency.)

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

• noun a military trainee (as at a military academy)