Princeton's WordNet

1. mucus, mucous secretion(noun)

   protective secretion of the mucus membranes; in the gut it lubricates the passage of food and protects the epithelial cells; in the nose and throat and lungs it can make it difficult for bacteria to penetrate the body through the epithelium

Wiktionary

1. mucus(Noun)

   A slippery secretion from the lining of the mucous membranes.

Origin: Borrowed from mucus.

Webster Dictionary

1. Mucus(noun)

   a viscid fluid secreted by mucous membranes, which it serves to moisten and protect. It covers the lining membranes of all the cavities which open externally, such as those of the mouth, nose, lungs, intestinal canal, urinary passages, etc

2. Mucus(noun)

   any other animal fluid of a viscid quality, as the synovial fluid, which lubricates the cavities of the joints; -- improperly so used

3. Mucus(noun)

   a gelatinous or slimy substance found in certain algae and other plants

U.S. National Library of Medicine

1. Mucus

   The viscous secretion of mucous membranes. It contains mucin, white blood cells, water, inorganic salts, and exfoliated cells.

• slymAfrikaans
• مُخاطArabic
• слузBulgarian
• mucoPortuguese (BR)
• hlenCzech
• der SchleimGerman
• slimDanish
• βλένναGreek
• mocoSpanish
• limaEstonian
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• sluz iz nosaCroatian
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• mucus; mucozitateRomanian
• слизьRussian
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• 身體產生的黏液(如鼻涕、痰)Chinese (Trad.)
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• مخاط، ایک چپچپا مادہUrdu
• nước nhầyVietnamese
• 身体产生的黏液（如鼻涕、痰）Chinese (Simp.)