• synonyms


[mil-doo, -dyoo]
See more synonyms for mildew on Thesaurus.com
  1. Plant Pathology. a disease of plants, characterized by a cottony, usually whitish coating on the surface of affected parts, caused by any of various fungi.
  2. any of these fungi.Compare downy mildew, powdery mildew.
  3. any of similar coatings or discolorations, caused by fungi, as that which appears on fabrics, paper, leather, etc., when exposed to moisture.
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verb (used with or without object)
  1. to affect or become affected with mildew.
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Origin of mildew

before 1000; Middle English: honeydew, mildew; Old English mildēaw, equivalent to mil- honey (cognate with Gothic milith, akin to Latin mel, Greek méli) + dēaw dew
Related formsmil·dew·y, adjectiveun·mil·dewed, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words

blight, mold, must, mould, mustiness

Examples from the Web for mildew

Historical Examples

  • The very spectacle of that form which I had learned to love is mildew and contagion to my eyes.


    William Godwin

  • Of these, mealy-bug, red-spider, thrips and mildew are most troublesome.

  • The only fungous disease of the grape troublesome in the greenhouse is mildew.

  • The vine is vigorous, hardy and productive but subject to mildew and rot.

  • The vine is vigorous, hardy and productive but susceptible to mildew.

British Dictionary definitions for mildew


  1. any of various diseases of plants that affect mainly the leaves and are caused by parasitic fungiSee also downy mildew, powdery mildew
  2. any fungus causing this kind of disease
  3. another name for mould 2
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  1. to affect or become affected with mildew
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Derived Formsmildewy, adjective

Word Origin

Old English mildēaw, from mil- honey (compare Latin mel, Greek mēli) + dēaw dew
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

Word Origin and History for mildew


mid-13c., mildeu "honeydew, nectar," from Old English meledeaw "honeydew" (sticky stuff exuded by aphids), from Proto-Germanic compound of *melith "honey" (see Melissa) + *dawwaz "dew" (see dew). Cf. Old Saxon milidou, Dutch meeldauw, German Meltau "mildew."

First element in many cases assimilated to forms of meal (n.2) "ground grain." As a kind of fungus it is first recorded mid-14c., so called from its being sticky and originally growing in plants. As a verb from 1550s. Related: Mildewed.

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Online Etymology Dictionary, © 2010 Douglas Harper

mildew in Science


  1. Any of various fungi or oomycete organisms that form a white or grayish coating on surfaces, such as plant leaves, cloth, or leather, especially under damp, warm conditions. Powdery mildews are important plant diseases usually caused by ascomycete fungi, while downy mildews, including a serious disease of grapevines, are caused by oomycetes.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.