Frontier

1. v. i. To constitute or form a frontier; to have a frontier; — with on.
2. 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.
3. n. An outwork.
4. a. Lying on the exterior part; bordering; conterminous; as, a frontier town.
5. a. Of or relating to a frontier.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.