Available Definitions:
1) interj. - Go well; good-by; adieu; -- originally applied to a person departing, but by custom now applied both to those who depart and those who remain. It is often separated by the pronoun; as, fare you well; and is sometimes used as an expression of separation only; as, farewell the year; farewell, ye sweet groves; that is, I bid you farewell.
2) n. - A wish of happiness or welfare at parting; the parting compliment; a good-by; adieu.
3) n. - Act of departure; leave-taking; a last look at, or reference to something.
4) a. - Parting; valedictory; final; as, a farewell discourse; his farewell bow.