frontier

American  

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

noun

frontiers plural

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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Synonym Usage

See boundary.

Other Word Forms

Derived Forms

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

Inflected Forms

Nouns

• frontiers
  plural

Etymology

Origin of frontier

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

Explanation

A frontier represents uncharted territory. It could be a remote piece of land or a new field of study, but if someone calls it "the frontier," you are challenged to explore it. The noun frontier has several meanings. It can refer to the wilderness at the edge of a settled area (picture covered wagons pushing westward) or it can mean a field of study that has not yet been explored (picture genetically engineering pet dinosaurs). Deriving from "the front line of an army," a frontier can be thought of as an offensive line in a battle — always pushing forward, trying to conquer new territory.

Example Sentences

See Examples For:

frontier frontiers

"The THz range represents the frontier between electronic and photonic technologies," explains Laplace.

From Science Daily ● Jul. 31, 2026

Titled "Pacing the Frontier," the petition requests "that the US government support an international effort to develop the technical and governance tools needed to deliberately pace the frontier of automated AI development."

From Barron's ● Jul. 31, 2026

Discarded flotation rings and clothes had been left on the shore near where the frontier barrier meets the sea.

From Barron's ● Jul. 30, 2026

Businesses are also pumping tens of billions into frontier AI models.

From The Wall Street Journal ● Jul. 30, 2026

Instead, Hoover created a pristine origin story, a founding mythology in which the bureau, under his direction, had emerged from lawlessness and overcome the last wild American frontier.

From "Killers of the Flower Moon" by David Grann

China’s Moonshot AI has launched an artificial-intelligence model it says outperforms some cutting-edge U.S. systems, the latest sign that Chinese labs can rival American counterparts in critical technology frontiers.

From The Wall Street Journal ● Jul. 17, 2026

Terry says Qantas is conquering "one of the last frontiers in commercial aviation".

From BBC ● Jun. 26, 2026

After IBM’s Deep Blue supercomputer scored a landmark victory over chess champion Garry Kasparov in 1997, researchers sought new simulations to push the frontiers of machine intelligence.

From MarketWatch ● May 23, 2026

"This study opens up new frontiers in research on human evolution," adds Professor Eleanor Scerri of the Max Planck Institute of Geoanthropology, also senior author of the study.

From Science Daily ● May 3, 2026

The frontiers between the three superstates are in some places arbitrary, and in others they fluctuate according to the fortunes of war, but in general they follow geographical lines.

From "1984" by George Orwell