lieutenant

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

• noun A commissioned rank in the US Navy or Coast Guard that is above lieutenant junior grade and below lieutenant commander.
• noun A first lieutenant.
• noun A second lieutenant.
• noun One who holds the rank of lieutenant, first lieutenant, or second lieutenant.
• noun A commissioned officer in the British and Canadian navies ranking just below a lieutenant commander.
• noun An officer in a police or fire department ranking below a captain.
• noun One who acts in place of or represents a superior; an assistant or deputy.

from The Century Dictionary.

• noun In archery, the winner of a lieutenancy in a shooting-match.
• noun In general, one who holds the place of another in the performance of any duty or function; one authorized to act in lieu of another, or employed to carry out his will or purposes; the substitute or representative of a superior.
• noun One who holds an office, civil or military, in subordination to or as the representative of a superior; an officer authorized to perform certain functions in the absence or under the orders of another: as, the lieutenant of the Tower of London; the lord lieutenant of Ireland or of an English county (considered the direct representative of the sovereign).

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

• noun An officer who supplies the place of a superior in his absence; a representative of, or substitute for, another in the performance of any duty.
• noun A commissioned officer in the army, next below a captain.
• noun A commissioned officer in the British navy, in rank next below a commander.
• noun A commissioned officer in the United States navy, in rank next below a lieutenant commander.
• noun [Eng.] the title of any one of the deputies or assistants of the lord lieutenant of a county.
• noun an army officer next in rank above major, and below colonel.
• noun an officer in the United States navy, in rank next below a commander and next above a lieutenant.
• noun See in Vocabulary.
• noun [U. S.], [Eng.] A deputy governor acting as the chief civil officer of one of several colonies under a governor general.

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

• noun military The lowest commissioned officer rank or ranks in many military forces.
• noun A person who executes the plans and directives of another.
• adjective A military grade that is junior to the grade the adjective modifies: lieutenant colonel, lieutenant general, lieutenant commander.

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

• noun a commissioned military officer
• noun an assistant with power to act when his superior is absent
• noun an officer in a police force
• noun an officer holding a commissioned rank in the United States Navy or the United States Coast Guard; below lieutenant commander and above lieutenant junior grade