mildew

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Any of various fungi that form a superficial, usually whitish growth on plants and various organic materials.
2. n. A superficial coating or discoloration of organic materials, such as cloth, paper, or leather, caused by fungi, especially under damp conditions.
3. n. A plant disease caused by such fungi.
4. v. To affect or become affected with mildew.

Century Dictionary and Cyclopedia

1. n. A minute parasitic fungus which frequently appears on the leaves, stems, and various other parts of plants or other decaying organic substances as a white frost-like down, or in spots or with various discolorations. The name is more properly restricted to the Erysipheæ, or powdery mildews, and the Peronosporeæ, or downy mildews. The Uredineæ, of which Puccinia graminis, the cornmildew of England, is the type, are more properly rusts. (See rust, Uredineæ.) The mildews are among the most destructive fungi known. Peronospora viticola is the very destructive American downy mildew of the grape, and Uncinula ampelopstdis, of which the so-called Oīdium Tuckeri is the conidial form, is the powdery mildew of the grape. Phytophthora infestans mildew of the potato, causing the disease known as potatorot. Erysiphe communis is a very common mildew on various Legvminosæ, Ranunculaceæ, etc. The so-called mildew of linen is produced by a species of Cladosporium. See Cladosporium, Erysipheæ Peronosporeæ.
2. n. A state of decay produced in living and dead vegetable matter, and in some manufactured products of vegetable matter, such as cloth and paper, by the ravages of very minute parasitical fungi.
3. To taint with mildew.
4. To become affected with mildew.
5. n. A disease of cucumbers, melons, pumpkins, and similar plants, caused by Plasmopara Cubensis.

Wiktionary

1. n. A growth of minute powdery or webby fungi, whitish or of different colors, found on various diseased or decaying substances.
2. v. transitive To taint with mildew.
3. v. intransitive To become tainted with mildew.

GNU Webster's 1913

1. n. (Bot.) A growth of minute powdery or webby fungi, whitish or of different colors, found on various diseased or decaying substances.
2. v. To taint with mildew.
3. v. To become tainted with mildew.

WordNet 3.0

1. n. the process of becoming mildewed
2. n. a fungus that produces a superficial (usually white) growth on organic matter
3. v. become moldy; spoil due to humidity