【释义】
the frontier, an area where people have never lived before, that not much is known about, especially in the western US before the 20th century
〔尤指 20 世纪前美国西部的〕边远地区，荒野地区; 边疆:
【例句】
a novel about a family's struggle on the American frontier
描写一家人在美国边远地区奋斗的小说
【例句】
space, the final frontier
太空，最后的前沿