Virus

Part of speech: noun (n.)

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

2. 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.

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