mildew

Mildew is a kind of fungus that grows in damp environments. If you find a white, musty-smelling powder on a book that's been stored in the basement, it's probably mildew. Yuck!

Mildew and mold are closely related — mildew is a less harmful kind of fungus, though both can cause breathing problems. While mildew is almost always white, mold is darker and fuzzier. Since dampness causes mildew to spread, keeping things dry (possibly with the help of a dehumidifier or air conditioner) can help prevent it. The stickiness of plant mildew helps explain the word's etymology. It comes from a root meaning "honeydew."

Definitions of mildew
  1. noun
    a fungus that produces a superficial (usually white) growth on organic matter
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    types:
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    powdery mildew
    any of various fungi of the genus Erysiphe producing powdery conidia on the host surface
    downy mildew, false mildew
    any of various fungi of the family Peronosporaceae parasitic on e.g. grapes and potatoes and melons
    Peronospora tabacina, blue mold fungus
    fungus causing a serious disease in tobacco plants characterized by bluish-grey mildew on undersides of leaves
    Peronospora destructor, onion mildew
    fungus causing a downy mildew on onions
    Peronospora hyoscyami, tobacco mildew
    fungus causing a downy mildew on growing tobacco
    type of:
    fungus
    an organism of the kingdom Fungi lacking chlorophyll and feeding on organic matter; ranging from unicellular or multicellular organisms to spore-bearing syncytia
  2. noun
    the process of becoming mildewed
    synonyms: mold, mould
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    type of:
    spoilage, spoiling
    the process of becoming spoiled
  3. verb
    become moldy; spoil due to humidity
    synonyms: mold
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    types:
    smut
    become affected with smut
    dry-rot
    affect or be affected with dry rot
    type of:
    change
    undergo a change; become different in essence; losing one's or its original nature
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