Entry 1 sense Webster, 1913 Gastro- · Gas·tro- · IPA /ˈɡæstɹoʊ-/ 01 A combining form from the Gr. �, �, the stomach, or belly; as in gastrocolic, gastrocele, gastrotomy. 1. A combining form from the Gr. �, �, the stomach, or belly; as in gastrocolic, gastrocele, gastrotomy.