frontier

American  

[fruhn-teer, fron-, fruhn-teer] / frʌnˈtɪər, frɒn-, ˈfrʌn tɪər /

noun

1. the part of a country that borders another country; boundary; border.

2. the land or territory that forms the furthest extent of a country's settled or inhabited regions.

3. Often frontiers.

   1. the limit of knowledge or the most advanced achievement in a particular field.

      the frontiers of physics.

   2. an outer limit in a field of endeavor, especially one in which the opportunities for research and development have not been exploited.

      the frontiers of space exploration.

4. Mathematics. boundary.

---

adjective

1. of, relating to, or located on the frontier.

   a frontier town.

frontier British  

/ frʌnˈtɪə, ˈfrʌntɪə /

noun

1. 1. the region of a country bordering on another or a line, barrier, etc, marking such a boundary

   2. ( as modifier )

      a frontier post

2. 1. the edge of the settled area of a country

   2. ( as modifier )

      the frontier spirit

3. (often plural) the limit of knowledge in a particular field

   the frontiers of physics have been pushed back

---

Related Words

See boundary.

Other Word Forms

• frontierless adjective
• frontierlike adjective
• semifrontier noun
• transfrontier adjective

Etymology

Origin of frontier

1350–1400; Middle English frounter < Old French frontier, equivalent to front (in the sense of opposite side; front ) + -ier -ier ²

Example Sentences

With stablecoins gaining a regulatory foothold, the next frontier is the financial infrastructure they power: tokenized assets, decentralized exchanges and new means of capital formation.

From The Wall Street Journal • Apr. 8, 2026

“This significant expansion of our compute infrastructure will power our frontier Claude models and help us serve extraordinary demand from customers worldwide,” Anthropic said in a blog post on Monday.

From Barron's • Apr. 7, 2026

"This paper represents a critical leap into a much larger, more exciting frontier."

From Science Daily • Apr. 7, 2026

At the time, however, the frontier – with its rugged cowboys, miners and railroad men – defined American manhood.

From Salon • Apr. 6, 2026

The local accent is barbed with a prairie twang, a ranch-hand nasalness, and the men, many of them, wear narrow frontier trousers, Stetsons, and high-heeled boots with pointed toes.

From "In Cold Blood" by Truman Capote