mildew

/ˌmɪlˈdu/

/ˈmɪldu/

Other forms: mildewed; mildews; mildewing

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
   types:

   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

   type of:

   spoilage, spoiling

   the process of becoming spoiled
3. verb

   become moldy; spoil due to humidity
   synonyms: mold

   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