Definition of: senior

(sēn′yər) adjective
1. Older in years; elder; specifically, after personal names (usually in the abbreviated form Sr.), to denote the elder of two related persons of the same name, especially a father and his son.
2. Older in office; more advanced in service; superior in rank or dignity.
3. Pertaining to the closing year of a high school or college course.
—noun
1. One older in years or office, or more advanced in rank or dignity than another.
2. Hence, any elderly person.
3. A member of a senior class.
4. A graduate or one of the older fellows of an English college. [<L, compar. of senex, senis old]