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

According to witnesses spoken to by AFP, thousands of people who flocked to the border town of Fnideq were not stopped by the authorities, even as they approached the frontier across wooded hills.

From Barron's ● Aug. 1, 2026

When he discovered that people were swimming across the frontier, he said, he took his children back home then returned alone to swim himself.

From Barron's ● Aug. 1, 2026

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

From Science Daily ● Jul. 31, 2026

Mahaney said investors are also reacting to little detail on how Meta’s progress is going with its frontier AI models.

From MarketWatch ● Jul. 30, 2026

Nowadays, Garden City, which was once a rather raucous frontier town, is quite subdued.

From "In Cold Blood" by Truman Capote

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

From BBC ● Jun. 26, 2026

US astronaut Christina Koch, the first woman to take part in a lunar mission, was on Wednesday named the winner of a top Spanish prize for having "helped extend the frontiers of humanity".

From Barron's ● Jun. 17, 2026

Readers willing to let some of the technical details wash over them are rewarded with a lively picture of the contemporary frontiers of science where, the authors argue, certainty does not belong.

From The Wall Street Journal ● May 19, 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

Bull stood there accepting the small hurts of the border skirmishes waged on four frontiers of his body.

From "The Great Santini" by Pat Conroy