mucus

noun

mu·​cus ˈmyü-kəs 

: a viscid slippery secretion that is usually rich in mucins and is produced by mucous membranes which it moistens and protects

Examples of mucus in a Sentence

Recent Examples on the Web

Some infections that cause brown mucus include:6 Bacterial bronchitis: This bacterial lung infection causes brown or yellow-green mucus. —Mark Gurarie, Health, 15 June 2025

About 80 percent of cases start with those skin and mucus membrane masses showing up in the second or third decade of life. —Eric Berger, ArsTechnica, 12 June 2025

One common symptom is your nose producing thick, discolored mucus that can run both directions from your nose, forward resulting in a runny nose and backward resulting in postnasal drip. —Bruce Y. Lee, Forbes.com, 31 May 2025

This type of bleeding happens when the cervix softens and dilates, causing the mucus plug (which helps protect the cervix) to fall out. —Lisa McCarty, SELF, 21 May 2025

Word History

Etymology

borrowed from Latin mūcus, muccus "nasal discharge," perhaps going back to *moukos, o-grade derivative of Indo-European *(s)muk- "nasal discharge," *(s)meuk- "undo, loosen, wipe off" — more at myxo-

Note: See note at myxo-.

First Known Use

1597, in the meaning defined above

Rhymes for mucus

• fucus
• mucous
• caducous
• sambucus
• submucous
• verrucous

Kids Definition

mucus

noun

mu·​cus ˈmyü-kəs 

: a slippery sticky substance produced especially by mucous membranes which it moistens and protects

Medical Definition

mucus

noun

mu·​cus ˈmyü-kəs 

: a viscid slippery secretion that is usually rich in mucins and is produced by mucous membranes which it moistens and protects