frontier
noun
fron·tier
ˌfrən-ˈtir 
ˈfrən-ˌtir,
frän-ˈtir,
ˈfrän-ˌtir
1
a
: a border between two countries
the frontier between Canada and the U.S.
b
obsolete
: a stronghold on a frontier
2
a
: a region that forms the margin of settled or developed territory
an expedition to explore the western frontier
b
: the farthermost limits of knowledge or achievement in a particular subject
frontiers in immunology
c
: a line of division between different or opposed things
… the frontiers separating science and the humanities …—
R. W. Clark
R. W. Clark
d
: a new field for exploitative or developmental activity
… the brain lies before us as one of the last scientific frontiers here on earth.—Robert Klitzman
Robert Klitzman
frontier
adjective
Examples of frontier in a Sentence
the frontier between Canada and the U.S.
They were sent on an expedition to explore the western frontier.
Recent Examples on the Web
Wolfram Indigenous Australian filmmaker Warwick Thornton’s new movie is billed as a period Western set on the 1930s colonial frontier.
—Andreas Wiseman, Deadline, 1 Jan. 2026
The wall, whose construction began in the year 122, was built to mark the northwestern boundary of the Roman Empire, serving as a frontier, customs post, and reminder of the reach of power.
—Rosa Lyster, Harpers Magazine, 30 Dec. 2025
But Fractyl is hardly alone in pursuing this therapeutic frontier.
—Elie Dolgin, IEEE Spectrum, 29 Dec. 2025
Even as America's western frontier was on the precipice of being overrun, this reporter had come to witness a run on the land.
—CBS News, 28 Dec. 2025
See All Example Sentences for frontier
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Andreas Wiseman, Deadline, 1 Jan. 2026
The wall, whose construction began in the year 122, was built to mark the northwestern boundary of the Roman Empire, serving as a frontier, customs post, and reminder of the reach of power.
—Rosa Lyster, Harpers Magazine, 30 Dec. 2025
But Fractyl is hardly alone in pursuing this therapeutic frontier.
—Elie Dolgin, IEEE Spectrum, 29 Dec. 2025
Even as America's western frontier was on the precipice of being overrun, this reporter had come to witness a run on the land.
—CBS News, 28 Dec. 2025
See All Example Sentences for frontier
Cite this Entry
“Frontier.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/frontier. Accessed 2 Jan. 2026.
Copy CitationKids Definition
frontier
noun
fron·tier
ˌfrən-ˈti(ə)r
frän-
frän-
1
: a border between two countries
2
a
: a region that forms the edge of the settled part of a country
b
: the outer limits of knowledge or achievement
the frontiers of science
frontier
adjective
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