The Collaborative International Dictionary
Gastro-
Gastro- \Gas"tro-\ A combining form from the Gr. ?, ?, the stomach, or belly; as in gastrocolic, gastrocele, gastrotomy.
Douglas Harper's Etymology Dictionary
gastro-
scientific word-forming element meaning "stomach," before vowels gastr-, from Greek gastro-, comb. form of gaster (genitive gastros) "belly, paunch" (see gastric).
Wiktionary
gastro-
pre. 1 Of or relating to the stomach. 2 Of or relating to cooking.
Wikipedia
Gastro-
Gastro- is a common English-language prefix derived from the ancient Greek gastros (" stomach"). It is used in many words.