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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.

Panama's Ministry of Culture said the discovery was "of great importance for Panamanian archaeology and the study of pre-Hispanic societies of the Central American isthmus," referring to the land that connects North and South America.

From Barron's • Feb. 21, 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 saying goes that almost every family here on the isthmus includes a person who identifies as muxe.

From Los Angeles Times • Jan. 11, 2024

The Chonhar bridge hit overnight is one of just a handful of access roads to Crimea, which is linked to the Ukrainian mainland by a narrow isthmus.

From Reuters • Jun. 22, 2023

Downcountry a storm had passed over the isthmus and leveled the dead black trees from east to west like weeds in the floor of a stream.

From "The Road" by Cormac McCarthy

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.