diadelphous Syllabification: (di·a·del·phous)Pronunciation: /ˌdīəˈdelfəs/Definition of diadelphous adjective Botany (of stamens) united by their filaments so as to form two groups. Origin: early 19th century: from di-1 'two' + Greek adelphos 'brother' + -ousdiadelphous in other Oxford dictionaries Definition of diadelphous in the British & World English dictionary