Mu"cus (mū"kŭs), n. [L. mucus, muccus; cf. mucere to be moldy or musty, Gr. my`xa mucus, and Skr. muc to release. Cf. Match for striking fire, Moist, Mucilage.]
1.
(Physiol.) 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. (Physiol.) Any other animal fluid of a viscid quality, as the synovial fluid, which lubricates the cavities of the joints; -- improperly so used.
3. (Bot.) A gelatinous or slimy substance found in certain algæ and other plants.
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