Definition of "metazoan" [met•a•zo•an]

• A multicellular animal of the subkingdom Metazoa, a division of the animal kingdom in traditional two-kingdom classification systems. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Consider two classes of transcription factors that are known to play crucial roles in metazoan development: the T-box proteins and the SOX proteins."
• "These proteins play essential roles in metazoan development and are considered part of the developmental toolkit as outlined by biologist Sean Carroll."
• "He briefly discusses a recent paper where "The authors concluded that gene loss had been a substantial factor in evolution, and that" the ancestral metazoan is likely to have been much more complex than was previously imagined. ""