The Collaborative International Dictionary of English v.0.48:

Peronosporaceae \Peronosporaceae\ prop. n.
   A natural family of parasitic fungi; the downy mildews.

   Syn: family Peronosporaceae.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Peronosporaceae
    n 1: parasitic fungi: downy mildews [syn: Peronosporaceae,
         family Peronosporaceae]