Emily Dickinson Lexicon

COAST, n. [L. costa, a rib, side or coast; W. côst; Fr. côte for coste; It. costa; Sp. costa; Port. id.; D. kust; G. küste. Hence to accost. See Class Gs, No. 18, 25, 67. The word properly signifies a side, limit, border, the exterior part, from extension.]

1. The exterior line, limit, or border of a country, as in Scripture: “From the river to the uttermost sea shall your coast be.” – Deut. xi. “And ships shall come from the coast of Chittim.” – Numb. xxiv. Hence the word may signify the whole country within certain limits. – Ex. x. 4.
2. The edge or margin of the land next to the sea; the sea-shore. This is the more common application of the word; and it seems to be used for sea-coast, the border of the sea. Hence it is never used for the bank of a river.
3. A side; applied to objects indefinitely, by Bacon and Newton. This is a correct use of the word, but now obsolete.
4. The country near the sea-shore; as, populous towns along the coast. The coast is clear, is a proverbial phrase signifying, the danger is over; the enemies have marched off, or left the coast. – Dryden.