metazoan

  1. Noun.  (zoology) Any animal that undergoes development from an embryo stage with three tissue layers, namely the ectoderm, mesoderm, and endoderm. The term applies to all animals except the sponges.
  2. Adjective.  Having to do with animals that develop from an embryo with three tissue layers.

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This entry was last updated on RefTopia from its source on 3/20/2012.