frontier
Americannoun
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the part of a country that borders another country; boundary; border.
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the land or territory that forms the furthest extent of a country's settled or inhabited regions.
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Often frontiers.
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the limit of knowledge or the most advanced achievement in a particular field.
the frontiers of physics.
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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.
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Mathematics. boundary.
adjective
noun
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the region of a country bordering on another or a line, barrier, etc, marking such a boundary
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( as modifier )
a frontier post
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the edge of the settled area of a country
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( as modifier )
the frontier spirit
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(often plural) the limit of knowledge in a particular field
the frontiers of physics have been pushed back
Synonym Usage
See boundary.
Other Word Forms
Derived Forms
Inflected Forms
Nouns
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.
Vocabulary lists containing frontier
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
"The frontier of AI has officially moved well past IMO math," Das wrote.
From Barron's ● Jul. 23, 2026
“It takes a trusted ecosystem of partners to help turn our frontier models and products into real business impact,” said Colleen Kapase, OpenAI’s vice president of global partnerships and ecosystem.
From The Wall Street Journal ● Jul. 22, 2026
“It’s fun to be at the frontier of the whole thing,” said an Alibaba business development manager at the company’s booth.
From The Wall Street Journal ● Jul. 20, 2026
“Running advanced frontier models with expansive context windows places immense pressure on memory and manufacturing pipelines,” DeYonker told MarketWatch in emailed comments.
From MarketWatch ● Jul. 20, 2026
Fort Hare had been founded in 1916 by Scottish missionaries on the site of what was the largest nineteenth-century frontier fort in the eastern Cape.
From "Long Walk to Freedom" by Nelson Mandela
In other words, if you want to be inspired by the frontiers of automotive engineering and solutions-based product design, look to China.
From The Wall Street Journal ● Jul. 11, 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
"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
“And if during the night at one of the frontiers the Customs officials should require a piece of luggage to be opened?”
From "Murder on the Orient Express" by Agatha Christie
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.