Webster's Revised Unabridged Dictionary · 1913

Farewell

Farewell , interjection

[Fare (thou, you) + well.]

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.
So farewell hope, and with hope, farewell fear. — Milton
Fare thee well! and if forever, Still forever fare thee well. — Byron

The primary accent is sometimes placed on the first syllable, especially in poetry.

Farewell , noun

1.
A wish of happiness or welfare at parting; the parting compliment; a good-by; adieu.
2.
Act of departure; leave-taking; a last look at, or reference to something.
And takes her farewell of the glorious sun. — Shakespeare
Before I take my farewell of the subject. — Addison

Farewell , adjective

Parting; valedictory; final; as, a farewell discourse; his farewell bow.
Leans in his spear to take his farewell view. — Tickell
Collocations (1)
Farewell rock (Mining) , the Millstone grit; -- so called because no coal is found worth working below this stratum. It is used for hearths of furnaces, having power to resist intense heat. — Ure