Virus

Contagious or poisonous matter, as of specific ulcers, the bite of snakes, etc.; -- applied to organic poisons.

The special contagion, inappreciable to the senses and acting in exceedingly minute quantities, by which a disease is introduced into the organism and maintained there.

Fig.: Any morbid corrupting quality in intellectual or moral conditions; something that poisons the mind or the soul; as, the virus of obscene books.

A small infectious agent that requires a host cell to reproduce

(virology) ultramicroscopic infectious agent that replicates itself only within cells of living hosts; many are pathogenic; a piece of nucleic acid (DNA or RNA) wrapped in a thin coat of protein

a software program capable of reproducing itself and usually capable of causing great harm to files or other programs on the same computer; "a true virus cannot spread to another computer without human assistance"

a harmful or corrupting agency; "bigotry is a virus that must not be allowed to spread"; "the virus of jealousy is latent in everyone"