frontier

Short definition from Wiktionary

Noun

1. 1
   The part of a country which borders or faces another country or unsettled region.
2. 2
   The most advanced or recent version of something; the leading edge.
3. 3
   An outwork of a fortification.

Verb

1. 1
   To live as pioneers on frontier territory.
2. 2
   To place on the frontier.

Proper noun

1. 1
   An unincorporated community in Koochiching County, Minnesota, United States, located on the Canadian border.
2. 2
   A city in North Dakota.
3. 3
   An unincorporated community in Lincoln County, Wyoming.
4. 4
   A village in Saskatchewan, Canada.
5. 5
   A rural municipality on the US border in south-west Saskatchewan, which includes the village; in full, the Rural Municipality of Frontier No. 19.