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 WordNet 3.0 & Open English WordNet

A lieutenant is a commissioned officer rank in the armed forces of many nations. Wikipedia

Military rank in many armies Wikidata

A Commissioned Officer in the United States Coast Guard, Public Health Service, or National Atmospheric and Oceanic Administration whose rank is above that of Ensign and below Lieutenant Commander. There are two ranks of lieutenant: Lieutenant Junior Grade and lieutenant. Wiktionary