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
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of, relating to, or located on the frontier.
a frontier town.
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
- 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; front ) + -ier -ier 2
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.
Suleyman handed over responsibilities for AI services, such as the expensive Microsoft 365 Copilot AI assistant, so that he could be laser-focused on new frontier models.
From Barron's • Apr. 4, 2026
Wrack said: "We have a masculinity crisis brewing in our schools. Teachers desperately need increased support to deal with this new frontier of behaviour management."
From BBC • Apr. 4, 2026
Meanwhile, Brazil’s planters mobilized more than one million slaves to settle frontier lands west of Rio de Janeiro, almost entirely to satisfy the North American demand for coffee.
From The Wall Street Journal • Apr. 3, 2026
Still, he was eager to explore a fresh frontier.
From Los Angeles Times • Apr. 1, 2026
Dressed in rugged deerskin hunting shirts, the Virginians met up with some locals from nearby Marblehead, Massachusetts, who made fun of the Virginians and their frontier outfits.
From "In the Shadow of Liberty" by Kenneth C. Davis
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.