The Collaborative International Dictionary of English v.0.48:

Myxomycetes \Myx`o*my*ce"tes\, n. pl. [NL.; Gr. ? mucus, slime +
   myceles.] (Bot.)
   A class of peculiar organisms, the slime molds, formerly
   regarded as animals (Mycetozoa), but now generally thought to
   be plants and often separated as a distinct phylum
   (Myxophyta); essentially equivalent to the division
   Myxomycota. They are found on damp earth and decaying
   vegetable matter, and consist of naked masses of protoplasm,
   often of considerable size, which creep very slowly over the
   surface and ingest solid food. -- Myx`o*my*ce"tous, a.

   Syn: true slime molds, acellular slime molds, plasmodial
        slime molds.
        [Webster 1913 Suppl. + WordNet 1.5]

WordNet (r) 3.0 (2006):

Myxomycetes
    n 1: the class of true slime molds; essentially equivalent to
         the division Myxomycota [syn: Myxomycetes, class
         Myxomycetes]