1. Any of various primitive organisms of the phylum Acrasiomycota, especially of the genus Dictyostelium, that grow on dung and decaying vegetation and have a life cycle characterized by a slimelike amoeboid stage and a multicellular reproductive stage. Also called cellular slime mold.
2. Any of various organisms of the phylum Myxomycota that grow on decaying vegetation and in moist soil and have a similar but more advanced life cycle. Also called myxomycete.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.