[n] an assistant with power to act when his superior is absent
[n] an officer in a police force
[n] a commissioned military officer
[n] an officer holding a commissioned rank in the United States Navy or Coast Guard; below lieutenant commander and above lieutenant junior grade
Misc. Definitions
\Lieu*ten"ant\ (l[-u]*t[e^]n"ant), n. [F., fr. lieu place + tenant holding, p. pr. of tenir to hold, L. tenere. See {Lieu}, and {Tenant}, and cf. {Locum Tenens}.]
1. 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. The lawful magistrate, who is the vicegerent or lieutenant of God. --Abp. Bramhall.
2. (a) A commissioned officer in the army, next below a captain. (b) A commissioned officer in the British navy, in rank next below a commander. (c) A commissioned officer in the United States navy, in rank next below a lieutenant commander. Note: Lieutenant is often used, either adjectively or in hyphened compounds, to denote an officer, in rank next below another, especially when the duties of the higher officer may devolve upon the lower one; as, lieutenant general, or lieutenant-general; lieutenant colonel, or lieutenant-colonel; lieutenant governor, etc. {Deputy lieutenant}, the title of any one of the deputies or assistants of the lord lieutenant of a county. [Eng.] {Lieutenant colonel}, an army officer next in rank above major, and below colonel. {Lieutenant commander}, an officer in the United States navy, in rank next below a commander and next above a lieutenant. {Lieutenant general}. See in Vocabulary. {Lieutenant governor}. (a) An officer of a State, being next in rank to the governor, and, in case of the death or resignation of the latter, himself acting as governor. [U. S.] (b) A deputy governor acting as the chief civil officer of one of several colonies under a governor general. [Eng.]