Emily Dickinson Lexicon

SEN-IOR, a. [see'nyor; L. senior, comp. of senex, old. Set Senate.]

Elder or older; but as an adjective, it usually signifies older in office; as, the senior pastor of a church, where there are colleagues; a senior counselor. In such use, senior has no reference to age, for a senior counselor may be, and often is the younger man.