n. 1 a deputy or substitute acting for a superior. 2 a an army officer next in rank below captain. b a naval officer next in rank below lieutenant commander. 3 US a police officer next in rank below captain. lieutenant colonel (or commander or general) officers ranking next below colonel, commander, or general. lieutenant-governor the acting or deputy governor of a State, province, etc., under a governor or Governor-General. Lieutenant of the Tower the acting commandant of the Tower of London. lieutenancy n. (pl. -ies).
[ ME f. OF (as LIEU, TENANT) ]