lieutenant

n. commissioned rank (Military); officer who holds the rank of lieutenant (Military); assistant, deputy

Lieutenant is a military, naval, paramilitary, fire service or police officer rank.Lieutenant may also appear as part of a title used in various other organizations with a codified command structure. It often designates someone who is "second-in-command," and as such, may precede the name of the rank directly above it. For example, a "Lieutenant Master" is likely to be second-in-command to the "Master" in an organization utilizing both such ranks. Notable uses include Lieutenant Governor in various governments, and Quebec lieutenant in Canadian politics.
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Noun
1. a commissioned military officer
(hypernym) commissioned military officer
(hyponym) first lieutenant
(classification) military, armed forces, armed services, military machine, war machine
2. an officer in a police force
(synonym) police lieutenant
(hypernym) lawman, law officer, peace officer
3. an assistant with power to act when his superior is absent
(synonym) deputy
(hypernym) assistant, helper, help, supporter
(hyponym) second-in-command
4. 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
(hypernym) commissioned naval officer
(classification) military, armed forces, armed services, military machine, war machine

n. first lieutenant, lieutenant, commissioned officer's rank (Military)

(n.)
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.
  

(n.)
A commissioned officer in the United States navy, in rank next below a lieutenant commander.
  

(n.)
A commissioned officer in the British navy, in rank next below a commander.
  

(n.)
A commissioned officer in the army, next below a captain.