noun

1. Obsolete venom, as of a snake
2. 1. any of a kingdom (Virus) of prokaryotes, usually ultramicroscopic, that consist of nucleic acid, either RNA or DNA, within a case of protein: they infect animals, plants, and bacteria and reproduce only within living cells: viruses are considered as being either living organisms or inert chemicals
   2. a disease caused by a virus
3. anything that corrupts or poisons the mind or character; evil or harmful influence
4. an unauthorized, disruptive set of instructions placed in a computer program, that leaves copies of itself in other programs and disks

Etymology: L, a slimy liquid, poison < IE base *weis-, to flow (used of foul or malodorous fluids) > ooze, weasel, Gr ios, poison