/looh ten"euhnt/ ; in Brit. use, except in the navy, /lef ten"euhnt/ , n.
1. Mil.
a. See first lieutenant .
b. See second lieutenant .
2. U.S. Navy. a commissioned officer ranking between lieutenant junior grade and lieutenant commander.
3. a person who holds an office, civil or military, in subordination to a superior for whom he or she acts: If he can't attend, he will send his lieutenant.
[ 1325-75; ME lieu tenant place-holding. See LOCUM TENENS, LIEU, TENANT ]