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

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 of frontier

• border

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

To that end, Jurin is building its own highly efficient, domain-specific foundation model—much of the frontier capability at a fraction of the compute cost, for customers who cannot, or will not, depend on a model owned in Washington or Beijing. — Jurin Ai Contributor, Forbes.com, 18 Aug. 2026

Tether’s applications are not going to deliver cutting-edge frontier models, of course. — Jeff John Roberts, Fortune, 17 Aug. 2026

But the real test is whether the ocean can become AI’s next computing frontier without becoming its next environmental problem. — Nir Kshetri, The Conversation, 17 Aug. 2026

The frontier lab has a stake in the company, and OpenAI CEO Sam Altman was also an early investor in SB Energy. — Samantha Subin, CNBC, 17 Aug. 2026

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