1.A large, closed, four-wheeled carriage, having doors in the sides, and generally a front and back seat inside, each for two persons, and an elevated outside seat in front for the driver. Note: Coaches have a variety of forms, and differ in respect to the number of persons they can carry. Mail coaches and tallyho coaches often have three or more seats inside, each for two or three persons, and seats outside, sometimes for twelve or more.
2.A special tutor who assists in preparing a student for examination. (Colloq.) "Wareham was studying for India with a Wancester coach."
3.(Naut.) A cabin on the after part of the quarter-deck, usually occupied by the captain. (Written also couch) (Obs.) "The commanders came on board and the council sat in the coach."
4.(Railroad) A first-class passenger car, as distinguished from a drawing-room car, sleeping car, etc. It is sometimes loosely applied to any passenger car.
5.One who coaches; specif. (sports), A trainer; one who assists in training individual athletes or the members of a sports team, or who performs other ancillary functions in sports; as, a third base coach.
...