The Collaborative International Dictionary of English v.0.48:

Uredo \U*re"do\, n. [L., a blast, blight, a burning itch, fr.
   urere to burn, to scorch.]
   [1913 Webster]
   1. (Bot.) One of the stages in the life history of certain
      rusts (order Uredinales), regarded at one time as a
      distinct genus. It is a summer stage preceding the
      teleutospore, or winter stage. See Uredinales, in the
      Supplement.
      [1913 Webster]

   2. (Med.) Nettle rash. See Urticaria.
      [1913 Webster]