diborane Syllabification: (di·bo·rane)Pronunciation: /dīˈbôrˌān/Definition of diborane noun Chemistry a poisonous, reactive gas made by the action of acids on some borides. It is the simplest of the boranes and is an example of electron-deficient bonding. Chemical formula: B2H6 diborane in other Oxford dictionaries Definition of diborane in the British & World English dictionary