frontier

noun

fron·tier | \ ˌfrən-ˈtir ,

ˈfrən-ˌtir , frän-ˈtir , ˈfrän-ˌtir

Definition of frontier

1a : a border between two countries the frontier between Canada and the U.S.

b obsolete : a stronghold on a frontier

2a : 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

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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

This isn’t Bieber’s first foray onto the frontier of Wearing Hotel Slippers Outside. — Cady Drell, Marie Claire, "In Defense of Justin Bieber Wearing Slippers Outside," 6 July 2018 Rohrabacher has been a relentless advocate, serving on the Science Committee in Congress and sharing its mission to push back the frontier of space. — Dale Neugebauer And Four Others, latimes.com, "The Dana Rohrabacher we know remains unchanged," 30 May 2018 Both sides have promised to avoid a hard border on the island -- which will become the frontier between the U.K. and EU. — Alex Morales, Bloomberg.com, "May Says Brexit Customs Backstop Plan Would be Time-Limited," 21 May 2018 Citing security concerns, Israel, which withdrew troops and settlers from Gaza in 2005, blockades the coastal territory, maintaining tight restrictions on the movement of Palestinians and goods across the frontier. — Anchorage Daily News, "Israeli forces kill at least 12 Palestinian protesters on Gaza border, medics say," 30 Mar. 2018 So ultimately, the powerful booster could be symbolic more than anything else, pushing the commercial frontier of spaceflight beyond low-Earth orbit and into deep space. — Eric Berger, Ars Technica, "Forget the Falcon Heavy’s payload and focus on where the rocket will go," 2 Feb. 2018 Croatia was the maritime frontier of the Cold War, since its long Adriatic coast is separated from Italy to the west by only 150 miles of water. — Larry Wolff, WSJ, "Croatia Offers Redemption for Eastern Europe," 13 July 2018 Other legislation passed this year suggests there are still new frontiers for those who wish to make breastfeeding easier and more accessible. — Rebecca Beitsch, The Christian Science Monitor, "All US states now allow breastfeeding in public," 13 July 2018 New England may still be the next U.S. frontier for legal cannabis; just don’t try shopping for it quite yet. — Washington Post, "For cannabis legalization in New England, it’s a slow burn," 30 June 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'frontier.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.