Definition of "bilaterian"

bilaterian

noun
plural bilaterians or bilateria
1. (zoology) Any animal that has bilateral symmetry, collectively grouped in the clade Bilateria.
  Quotations
  Whatever the phylogenetic relationship among bilaterians and the diploblastic phyla, there was clearly a significant expansion in genomic information within the internode that connects the bilaterian clade to other branches.
  2005, N. S. Sharma, Continuity And Evolution Of Animals‎, page 91
  Lacking body cavities and both circulatory and excretory organs, with subepidermal nerve plexuses and 'brains' represented, if at all, by thickened anterior commissures, and with simple reproductive set-ups, acoels come close to representing a model stem ancestor for bilaterians.
  2007, J. W. Valentine, “Seeing ghosts: Neoproterozoic bilaterian body plans”, in Patricia Vickers-Rich, Patricia Komarower, editors, The Rise and Fall of the Ediacaran Biota, page 372
  In most bilaterians, the gut musculature and most vascular muscles derive from the mesoderm.
  2010, José Xavier-Neto, Marcos Sawada Simoes-Costa, Rodrigo Abe Castro, Hozana Andrade Castillo, Allysson Coelho Sampaio, Ana Paula Azambuja, “Chapter 1.1: Evolutionary Origins of Hearts”, in Nadia Rosenthal, Richard P. Harvey, editors, Heart Development and Regeneration, volume 1, page 12