Any weapon usable in biological warfare WordNet 3.0 & Open English WordNet

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. OmegaWiki

Any weapon designed to be used in biological warfare. Wiktionary

Weapon designed for use in biological warfare. Wiktionary (translation)