Definition of senior

• a. - More advanced than another in age; prior in age; elder; hence, more advanced in dignity, rank, or office; superior; as, senior member; senior counsel.
• a. - Belonging to the final year of the regular course in American colleges, or in professional schools.
• n. - A person who is older than another; one more advanced in life.
• n. - One older in office, or whose entrance upon office was anterior to that of another; one prior in grade.
• n. - An aged person; an older.
• n. - One in the fourth or final year of his collegiate course at an American college; -- originally called senior sophister; also, one in the last year of the course at a professional schools or at a seminary.