Living organisms (or infective material derived from them) which are intended to cause disease or death in animals, plants, or man, and which depend for their effects on their ability to multiply in the person, animal or plant attacked. Various living organisms (for example, rickettsiae, viruses and fungi), as well as bacteria, can be used as weapons.
any weapon usable in biological warfare; "they feared use of the smallpox virus as a bioweapon"