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

Bots paying other bots are a new frontier for the payments industry that needs new rails. —David G.w. Birch, Forbes.com, 24 May 2025

Longevity Lifestyle Coaches Matt Britton, CEO of Suzy and a leading AI and consumer trend expert advising Fortune 500 brands, sees health as a frontier for job creation. —Melissa Fleur Afshar, MSNBC Newsweek, 23 May 2025

The kingdom, which was closed to international tourists just a few years ago, is emerging as luxury travel’s new frontier, blending centuries-old heritage with cutting-edge sustainable design and five-star hospitality. —Ritu Upadhyay, Footwear News, 21 May 2025

The serious implication of it in the context of a Western, regarding the frontier as a place where state power is unformed, loose, and dubious, remains anecdotal and undeveloped. —Richard Brody, New Yorker, 20 May 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

Rhymes for frontier

• adhere
• ameer
• amir
• appear
• arrear
• astir
• austere
• career
• cashier
• cohere
• compere
• emir

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