E. co·li (? k??l?)n. A bacterium (Escherichia coli) normally found in the human gastrointestinal tract and existing as numerous strains, some of which are responsible for diarrheal diseases. Some strains have been used experimentally as model organisms for the study of biochemistry, molecular biology, and genetics.[New Latin E(scherichia) col?, species name : after Theodor Escherich (1857-1911), German physician + Latin col?, genitive of colon, colon; see colon2.]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.E. coli (?i??k??la?) n (Microbiology) short for Escherichia coli; see EscherichiaCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014