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  

/ ˈfrʌntɪə, frʌnˈtɪə /

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

“OpenAI and other frontier companies should not move forward with developments that further decrease” the ability to monitor AI.

From The Wall Street Journal ● Oct. 7, 2026

Smaller companies seeking equity capital are being crowded out by larger issuances, Kerr said—including the possible November listing of frontier AI model maker Anthropic.

From The Wall Street Journal ● Oct. 6, 2026

EU chief Ursula von der Leyen has proposed talks with the main frontier labs to "pace" the technology's growth, arguing the AI Act puts Europe "in the position to shape global efforts" at regulation.

From Barron's ● Oct. 6, 2026

It feels significant that the former Google boss has chosen someone with that experience to run his news teams, raising questions around how AI could open up the next frontier of a modern newsroom.

From BBC ● Oct. 5, 2026

If he’d wanted wide open spaces and silence, he would have stayed on the frontier and become the farmer his father had hoped for.

From "Six of Crows" by Leigh Bardugo

Actually, I take that back – consulting her most devoted fans will open new frontiers for you.

From Salon ● Aug. 29, 2026

Srinivasan is an advocate of boosting Earth’s birthrate, in part to settle new frontiers.

From The Wall Street Journal ● Aug. 1, 2026

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

His mind, in the words of one biographer, was "always operating out towards the frontiers, as far as he could see, and that was a great deal further than most other men."

From "A Short History of Nearly Everything" by Bill Bryson