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

Kevin Bryan, an associate professor at the University of Toronto specializing in innovation, defended Anthropic and said the fears about the risks of frontier intelligence being open source are real and widely shared.

From The Wall Street Journal ● Jul. 29, 2026

“The frontier labs are hoarding intelligence,” said Mahesh Lambe, an AI researcher who attended the protest.

From The Wall Street Journal ● Jul. 29, 2026

Lee noted that Microsoft is pursuing a broader strategy around proprietary AI models, expanding its frontier AI partners and vertically integrating infrastructure that spans cloud, data, security and application layers.

From MarketWatch ● Jul. 28, 2026

The tech industry’s letter urged policymakers to keep “the frontier plural by avoiding premature restrictions on open models that stifle competition or drive innovation overseas.”

From MarketWatch ● Jul. 24, 2026

On June 7, 1790, Secretary of War Henry Knox told an army commander that the frontier was so extensive that it would be “altogether impossible” to defend.

From "An Indigenous People’s History of the United States" by Roxanne Dunbar-Ortiz

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

From BBC ● Jun. 26, 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

Pyongyang closed its borders in January 2020 to stop the spread of the coronavirus, with research and media reports indicating that the diplomatically isolated nation spent subsequent years bolstering security along its frontiers.

From Barron's ● Apr. 28, 2026

Others — often referred to as “me too” drugs — are chemically or mechanistically similar to existing therapies, designed to compete within established categories rather than to open new frontiers.

From MarketWatch ● Apr. 15, 2026

A new kind of hero emerged as well—a hero willing to sacrifice self to explore new frontiers.

From "Women in Space" by Karen Bush Gibson