• 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 software program capable of reproducing itself and usually capable of causing great harm to files or other programs on the same computer

  Example: "A true virus cannot spread to another computer without human assistance"

• noun:   a harmful or corrupting agency

  Example: "Bigotry is a virus that must not be allowed to spread"

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