adenocarcinoma Syllabification: (ad·e·no·car·ci·no·ma)Pronunciation: /ˌadn-ōˌkärsəˈnōmə/Definition of adenocarcinoma noun (plural adenocarcinomas or adenocarcinomata /-ˈnōmətə/) Medicine a malignant tumor formed from glandular structures in epithelial tissue. adenocarcinoma in other Oxford dictionaries Definition of adenocarcinoma in the British & World English dictionary