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
Related Words
See boundary.
Other Word Forms
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
The Vocabulary.com Top 1000
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Maus I: My Father Bleeds History
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Human Geography - Middle School
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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.
Chief among them is their shared 4,300km border, previously a frontier for insecurity.
From BBC • May 18, 2026
The company’s chips can quickly perform the heavy duty mathematics of AI computing, and CEO Andrew Feldman plans to serve the biggest frontier models on earth.
From Barron's • May 15, 2026
Apple, which is deploying and testing frontier AI models to test and patch vulnerabilities, is reviewing the Calif report to validate its findings.
From The Wall Street Journal • May 14, 2026
Visit the American frontier, 1930s New York and the mountains of Europe.
From Los Angeles Times • May 13, 2026
Our new home was one of the oldest buildings in town, Mom proudly told us, with a real frontier quality to it.
From "The Glass Castle" by Jeannette Walls
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.
