virus

(noun) (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.

(noun) a harmful or corrupting agency. Examples: "Bigotry is a virus that must not be allowed to spread." "The virus of jealousy is latent in everyone."

(noun) a software program capable of reproducing itself and usually capable of causing great harm to files or other programs on the same computer. Synonyms: computer virus. Example: "A true virus cannot spread to another computer without human assistance."