cad·her·in (k?d-hîr??n)n. Any of a group of proteins that span the plasma membrane of eukaryotic cells and, in the presence of calcium, bind to identical proteins in adjacent cells, thus linking cells together in tissues.[Blend of ca(lcium) + adher(e) + -in.]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.