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

were sent on 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

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

frontier adjective

Synonyms

• border
• borderland
• march

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

From customer support to automating business operations, AI Integrations is accelerating businesses to the final frontier of digital evolution. —Jason Phillips, USA TODAY, 15 Feb. 2025

The Sabra situation mainly highlights the sharp contrast between the woolly frontiers of Marvel Comics and the frictionless corporate oversight of Marvel Studios. —Darren Franich, Vulture, 14 Feb. 2025

Location sharing is the final frontier in digital expressions of coupledom. —Shivani Vora, New York Times, 14 Feb. 2025

Their ventures are democratizing access to space, paving the way for future generations of astronauts, and opening up new frontiers for scientific discovery. —Dan Perry, Newsweek, 13 Feb. 2025

Word History

Etymology

Middle English fronter, from Anglo-French frountere, fronter, from front

First Known Use

15th century, in the meaning defined at sense 1a

Kids Definition

frontier

noun

fron·​tier ˌfrən-ˈti(ə)r  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