Source : Webster's Revised Unabridged Dictionary (1913)

Mildew \Mil"dew\, n. [AS. melede['a]w; akin to OHG. militou, G.
   mehlthau, mehltau; prob. orig. meaning, honeydew; cf. Goth.
   milip honey. See {Mellifluous}, and {Dew}.] (Bot.)
   A growth of minute powdery or webby fungi, whitish or of
   different colors, found on various diseased or decaying
   substances.

Mildew \Mil"dew\, v. t. [imp. & p. p. {Mildewed}; p. pr. & vb.
   n. {Mildewing}.]
   To taint with mildew.

         He . . . mildews the white wheat.        --Shak.

Mildew \Mil"dew\, v. i.
   To become tainted with mildew.

Source : WordNet®

mildew
     n 1: the process of becoming mildewed [syn: {mold}]
     2: a fungus that produces a superficial (usually white) growth
        on organic matter
     v : become moldy; spoil due to humidity; "The furniture molded
         in the old house" [syn: {mold}]