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.

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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

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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

Following the success of injectables, pills have become the next frontier.

From Barron's • Apr. 9, 2026

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

From Science Daily • Apr. 7, 2026

Dog poo bags are not the only indignity the famous defensive frontier has to endure.

From BBC • Apr. 6, 2026

When it was finished, when the pause had been politely respected as the frontier of the story, Billy Buck stood up and stretched and hitched his trousers.

From "The Red Pony" by John Steinbeck