Pronunciation: (frun-tēr', fron-; also, esp. Brit., frun'tēr),[key] —n. 1. the part of a country that borders another country; boundary; border.
2. the land or territory that forms the furthest extent of a country's settled or inhabited regions.
3. Often, frontiers. a. the limit of knowledge or the most advanced achievement in a particular field: the frontiers of physics. b. an outer limit in a field of endeavor, esp. one in which the opportunities for research and development have not been exploited: the frontiers of space exploration. 4. Math.boundary (def. 2).
—adj. of, pertaining to, or located on the frontier: a frontier town.