the border, confine, or extreme of a kingdom or province. Thus we say, a frontier town, frontier province, &c. Frontiers were anciently called marches.

The word is derived from the French frontière, and that from the Latin frontaria, as being a kind of front opposed to the enemy. Skinner derives frontier from front, because the frontier is the exterior and most advanced part of a state, as the front is that of the face of man.