The expedition mapped the rugged frontier between the two nations, documenting its rivers and mountain passes.
探险队绘制了两国之间崎岖边界的详细地图，记录了其河流和山口。
Which choice best defines “frontier”?
B — Border between countries, limits. “frontier” means border between countries, limits.
Which word means “border between countries, limits”?
D — frontier. “frontier” means border between countries, limits.
frontier — border between countries, limits. In Chinese: 边界，前沿.
frontier is pronounced /frʌnˈtɪr/.
The expedition mapped the rugged frontier between the two nations, documenting its rivers and mountain passes. (探险队绘制了两国之间崎岖边界的详细地图，记录了其河流和山口。)
border, boundary, limit — all close in meaning to frontier (border between countries, limits).
interior, center — each the opposite of frontier (border between countries, limits).
Yes. frontier is on the SAT Prep Basic list — the everyday academic words the SAT assumes you already have. The Digital SAT does not test vocabulary in isolation; words like this one are tested through Words in Context questions, where you choose the word that completes a passage most logically and precisely.
front(in front)+ier(noun).