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Synonyms

isthmus

American  
[is-muhs] / ˈɪs məs /

noun

plural

isthmuses, isthmi

  1. a narrow strip of land, bordered on both sides by water, connecting two larger bodies of land.

  2. Anatomy, Zoology. a connecting, usually narrow, part, organ, or passage, especially when joining structures or cavities larger than itself.

  3. Ichthyology. the narrow fleshy area between the sides of the lower jaw of a fish.

isthmus British  
/ ˈɪsməs /

noun

  1. a narrow strip of land connecting two relatively large land areas

  2. anatomy

    1. a narrow band of tissue connecting two larger parts of a structure

    2. a narrow passage connecting two cavities

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
isthmus Scientific  
/ ĭs′məs /

plural

isthmuses

  1. A narrow strip of land connecting two larger masses of land.

isthmus Cultural  

  1. A narrow strip of land that connects two larger bodies of land and has water on both sides.

Other Word Forms

  • isthmoid adjective

Etymology

Origin of isthmus

1545–55; < Latin < Greek isthmós neck (of land)

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Roosevelt was intrigued by the military and commercial possibilities of a canal across the isthmus, cutting 8,000 miles off a New York-San Francisco voyage.

From Barron's • Jan. 18, 2026

Paterson persuaded the Scottish parliament to establish a new enterprise based on England’s East India Company to found a Scottish colony on the narrow isthmus joining North and South America.

From The Wall Street Journal • Nov. 30, 2025

The waterway was cleaved across the most narrow section of the Panamanian isthmus in the late 1800s and early 1900s, by French and then U.S. engineers.

From Los Angeles Times • Jan. 31, 2025

It is known as the 'gap' on Panama's Darien isthmus because it is the only missing section, running about 60 miles, on the Pan-American highway that stretches from Alaska to Argentina.

From Reuters • Jul. 22, 2023

The latter desert separated advanced human societies of Mesoamerica from those of North America, while the isthmus separated advanced societies of Mesoamerica from those of the Andes and Amazonia.

From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.