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.

---

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

---

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

Many states are trying to crack down on the newest frontier in the financial wild west: prediction markets.

From Salon • May 24, 2026

We believe that space represents the largest economic frontier in human history.

From Barron's • May 23, 2026

They recognized that massive computing firepower would be needed to build and maintain frontier AI models and that potentially billions of dollars in fundraising would be necessary to move AI technology forward.

From The Wall Street Journal • May 20, 2026

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 Ulster Scots became the core group of frontier settlers in North America.

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