[lieu.ten.ant] n [ME, fr. MF, fr. lieu + tenant holding, fr. tenir to hold, fr. L tenere--more at thin] (14c) 1 a: an official empowered to act for a higher official b: an aide or representative of another in the performance of duty: assistant
2. a (1): first lieutenant (2): second lieutenant b: a commissioned officer in the navy or coast guard ranking above a lieutenant junior grade and below a lieutenant commander c: a fire or police department officer ranking below a captain