frontier

1.[c]国界；边界；边境a line that separates two countries, etc.; the land near this line

2.[sing]（尤指 19 世纪美国西部的）开发地区边缘地带，边远地区the edge of land where people live and have built towns, beyond which the country is wild and unknown, especially in the western US in the 19th century

3.[c][usupl]~ (of sth)（学科或活动的）尖端，边缘the limit of sth, especially the limit of what is known about a particular subject or activity

1.边疆;边界,边缘

2.新开辟地,边地;〈美〉边疆城市

3.(知识等的)尚待开发的领域

1.边疆的

2.新垦地的,边地的

1.a border between two countries, especially one with official points where people or vehicles cross; the outer edge of a country or area that is the farthest point where people have started to live and build towns; the western edge of the U.S. that Europeans had reached in the 17th, 18th, and 19th centuries; on or relating to a frontier

2.the most advanced or recent ideas about something