[ mil-doo, -dyoo ]
See synonyms for: mildewmildewedmildewingmildewy on

  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.

  1. any of similar coatings or discolorations, caused by fungi, as that which appears on fabrics, paper, leather, etc., when exposed to moisture.

verb (used with or without object)
  1. to affect or become affected with mildew.

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) + dēawdew

Other words from mildew

  • mildewy, adjective
  • un·mil·dewed, adjective

Words Nearby mildew Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use mildew in a sentence

British Dictionary definitions for mildew


/ (ˈmɪlˌdjuː) /

  1. any of various diseases of plants that affect mainly the leaves and are caused by parasitic fungi: See also downy mildew, powdery mildew

  2. any fungus causing this kind of disease

  1. another name for mould 2

  1. to affect or become affected with mildew

Origin of mildew

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

Derived forms of mildew

  • mildewy, adjective

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

Scientific definitions for mildew


[ mĭldōō′ ]

  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.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.