cho·le·cys·to·ki·nin (<A HREF="http://www.atomica.com/lookup_a6/pronkey.html">ko'li-sis't?-ki'nin</A>) n. (Abbr. CCK)A hormone produced principally by the small intestine in response to the presence of fats, causing contraction of the gallbladder, release of bile, and secretion of pancreatic digestive enzymes. Also called: pancreozymin