C. el·e·gans (s?? ?l??-g?nz)n. A nematode (Caenorhabditis elegans) that was the first animal whose genome was completely sequenced and is widely studied by researchers because it has a small genome and transparent skin.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.