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; 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

Episodic television represents a new frontier for Cage, an actor who, despite having a fabulously eclectic body of work to his name, had not embraced the small screen.

From Los Angeles Times • May 20, 2026

The Enhanced Games will showcase a new frontier for self-optimisation and the use of science to push biological boundaries.

From BBC • May 20, 2026

According to the company, when looking at output tokens per second, Gemini 3.5 Flash is four times faster than other frontier models.

From Barron's • May 19, 2026

“We are super focused on bringing that frontier capability of agents safely and securely to consumers so that they work for everyone.”

From The Wall Street Journal • May 19, 2026

Blood rushed to my brain; I felt an animating surge of adrenaline, of possibility, of a frontier being pushed outward.

From "Educated" by Tara Westover