Frontier Fron"tier, v. i. To constitute or form a frontier; to have a frontier; -- with on. [Obs.] --Sir W. Temple., Frontier Fron"tier, n. [F. fronti[`e]re, LL. frontaria. See Front.] 1. 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. (Fort.) An outwork. [Obs.] Palisadoes, frontiers, parapets. --Shak., Frontier Fron"tier, a. 1. Lying on the exterior part; bordering; conterminous; as, a frontier town. 2. Of or relating to a frontier. ``Frontier experience.' --W. Irving.