bioweapon UK /ˈbaɪ.əʊˌwɛ.pən/US /ˈbaɪ.oʊˌwɛ.pən/ noun1 •Any weapon designed to be used in biological warfare.And (Wouter) Basson (who had worked on South Africa's clandestine bioweapons program) was there, too. — 2009 formsbioweapons