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mucus

American  
[myoo-kuhs] / ˈmyu kəs /

noun

  1. a viscous, slimy mixture of mucins, water, electrolytes, epithelial cells, and leukocytes that is secreted by glands lining the nasal, esophageal, and other body cavities and serves primarily to protect and lubricate surfaces.

mucus British  
/ ˈmjuːkəs /

noun

  1. the slimy protective secretion of the mucous membranes, consisting mainly of mucin

"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
mucus Scientific  
/ myo̅o̅′kəs /

  1. The slimy, viscous substance secreted as a protective lubricant by mucous membranes. Mucus is composed chiefly of large glycoproteins called mucins and inorganic salts suspended in water.

mucus Cultural  

  1. A slippery and somewhat sticky fluid secreted by the glands in mucous membranes. Mucus lubricates and protects the mucous membranes.

Etymology

Origin of mucus

1655–65; < Latin mūcus snot; akin to Greek myktḗr nose, mýxa slime

Compare meaning

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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.

Born with cystic fibrosis, a genetic disorder that causes mucus to become thick and sticky, she has just 9% lung function.

From BBC • Mar. 24, 2026

CF is a genetic condition that can particularly affect someone's digestive system, as well as their lungs, because their body produces a thick, sticky mucus that coats the organs.

From BBC • Mar. 20, 2026

Unvaccinated mice developed a strong Th2 response and accumulated mucus in their airways.

From Science Daily • Feb. 23, 2026

Instead of focusing only on gut movement, future therapies may aim to protect the colon's mucus barrier and address the underlying microbial cause.

From Science Daily • Feb. 19, 2026

“The trial,” I start to say, looking over at Barb and holding up my hand to pause the conversation as I cough up a wad of mucus.

From "Five Feet Apart" by Rachael Lippincott

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.