frontier
/ˈfrʌnˌtɪə(r)/noun
1- a line or border separating two countries边境, 边界。
1.1
- the district near such a line边疆。
1.2
- the extreme limit of settled land beyond which lies wilderness, especially referring to the western US before Pacific settlement（靠近荒野的定居地的）边缘地带, 边远地区, 边疆（尤指美国人在太平洋沿岸定居之前的西部）：
his novel of the American frontier.
他写的关于美国西部边疆开拓的小说。
1.3
- the extreme limit of understanding or achievement in a particular area（某一学科）的知识（或成就）边缘, 前沿, 新领域：
the success of science in extending the frontiers of knowledge.
科学在开拓知识新领域方面所取得的成功。
派生词
frontierless
adjective词源
late Middle English: from Old French frontiere, based on Latin frons， front- 'front'.