Possible Definitions:
1. Frontier (n.) That part of a country which fronts or faces another country or an unsettled region; the marches; the border, confine, or extreme part of a country, bordering on another country; the border of the settled and cultivated part of a country; as, the frontier of civilization.
2. Frontier (n.) An outwork.
3. Frontier (a.) Lying on the exterior part; bordering; conterminous; as, a frontier town.
4. Frontier (a.) Of or relating to a frontier.
5. Frontier (v. i.) To constitute or form a frontier; to have a frontier; -- with on.
