Senior \Sen"ior\, a. [L. senior, compar. of senex, gen. senis, old. See {Sir}.] 1. More advanced than another in age; prior in age; elder; hence, more advanced in dignity, rank, or office; superior; as, senior member; senior counsel. [1913 Webster] 2. Belonging to the final year of the regular course in American colleges, or in professional schools. [1913 Webster]