adj. & n.
adj. 1 (often foll. by to) more or most advanced in age or standing. 2 of high or highest position. 3 (placed after a person's name) senior to another of the same name. 4 (of a school) having pupils in an older age-range (esp. over 11). 5 US of the final year at a university, high school, etc.
n. 1 a person of advanced age or comparatively long service etc. 2 one's elder, or one's superior in length of service, membership, etc. (is my senior). 3 a senior student. senior citizen an elderly person, esp. an old-age pensioner. senior college US a college in which the last two years' work for a bachelor's degree is done. senior common (or combination) room Brit. a room for use by senior members of a college. senior nursing officer the person in charge of nursing services in a hospital. senior officer an officer to whom a junior is responsible. senior partner the head of a firm. senior service Brit. the Royal Navy as opposed to the Army. senior tutor Brit. a college tutor in charge of the teaching arrangements. seniority n.
[ ME f. L, = older, older man, compar. of senex senis old man, old ]