Hydrogen oxide Share definition Flag A scientific word for water. H2O. Not to be confused with deuterium oxide, which is heavy water (D2O). A: I filled these ballons with hydrogen oxide. B:What's that? A:It's water. Hydrogen oxide by HawaiianPunch1 July 31, 2010 0 0 Get merch Get the Hydrogen oxide mug. Buy Now — $32.95 See more merch