Whether in the human body or on a computer, a virus is a disease-causing agent. If you come down with a nasty stomach virus, be sure to drink lots of water, get lots of rest, and stay near the toilet.

Virus comes from a Latin word that was spelled the same way. It specifically referred to the poisonous sap of certain plants, which explains why it sounds similar to viscous, a word meaning "sticky." Nowadays, it’s used to describe something that causes infectious diseases, specifically a tiny, self-replicating agent made up of genetic material and protein.

Definitions of virus
  1. 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
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    arborvirus, arbovirus
    a large heterogeneous group of RNA viruses divisible into groups on the basis of the virions; they have been recovered from arthropods, bats, and rodents; most are borne by arthropods; they are linked by the epidemiologic concept of transmission between vertebrate hosts by arthropod vectors (mosquitoes, ticks, sandflies, midges, etc.) that feed on blood; they can cause mild fevers, hepatitis, hemorrhagic fever, and encephalitis
    bacteriophage, phage
    a virus that is parasitic (reproduces itself) in bacteria
    plant virus
    a plant pathogen that is a virus consisting of a single strand of RNA
    animal virus
    an animal pathogen that is a virus
    slow virus
    a virus that remains dormant in the body for a long time before symptoms appear
    tumor virus
    a cell-free filtrate held to be a virus responsible for a specific neoplasm
    (genetics) a virus or other agent that is used to deliver DNA to a cell
    any of a group of viruses including those that in humans cause upper respiratory infections or infectious pinkeye
    animal viruses belonging to the family Arenaviridae
    a large family of arboviruses that affect a wide range of hosts (mainly vertebrates and arthropods)
    an animal virus belonging to the family Bunyaviridae; can be used as a bioweapon
    animal viruses belonging to the family Filoviridae
    a family of arboviruses carried by arthropods
    an arbovirus of the family Togaviridae that can cause a variety of encephalitis in horses
    a family of arboviruses carried by arthropods
    animal viruses belonging to the family Flaviviridae
    a family of arborviruses carried by arthropods
    a family of arborviruses carried by arthropods
    an animal virus that causes vesicular stomatitis
    a family of arboviruses carried by arthropods
    any of a group of viruses that can cause pox diseases in vertebrates
    TMV, tobacco mosaic virus
    the widely studied plant virus that causes tobacco mosaic; it was the first virus discovered (1892)
    viroid, virusoid
    the smallest of viruses; a plant virus with its RNA arranged in a circular chromosome without a protein coat
    a bacteriophage that infects the bacterium Escherichia coli
    typhoid bacteriophage
    a bacteriophage specific for the bacterium Salmonella typhi
    a group of animal DNA viruses including viruses of ducks and woodchucks and squirrels and others as well as the virus causing hepatitis B in humans
    any of a group of viruses that contain two single-strand linear RNA molecules per virion and reverse transcriptase (RNA to DNA); the virus transcribes its RNA into a cDNA provirus that is then incorporated into the host cell
    any of a group of RNA viruses including those that cause influenza and mumps
    a group of single-strand RNA viruses with a protein coat
    herpes, herpes virus
    any of the animal viruses that cause painful blisters on the skin
    any of a group of animal viruses associated with or causing papillomas or polyomas
    any of a group of arboviruses including those causing rabies
    a neurotropic non-arbovirus of the family Rhabdoviridae that causes rabies
    any of a group of non-arboviruses including the rotavirus causing infant enteritis
    parvo, parvovirus
    any of a group of viruses containing DNA in an icosahedral protein shell and causing disease in dogs and cattle; not known to be associated with any human disease
    onion yellow-dwarf virus
    the virus that produces stunting and yellowing of the leaves of onion plants
    potato yellow-dwarf virus
    the virus that produces stunting and yellowing of the leaves of potato plants
    WTV, wound tumor virus
    a tumor virus transmitted by leafhoppers
    (genetics) a large vector that is made from a bacteriophage and used to clone genes or gene fragments
    type of:
    micro-organism, microorganism
    any organism of microscopic size
    infectious agent, infective agent
    an agent capable of producing infection
  2. noun
    a harmful or corrupting agency
    “bigotry is a virus that must not be allowed to spread”
    “the virus of jealousy is latent in everyone”
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    type of:
    agency, delegacy, representation
    the state of serving as an official and authorized delegate or agent
  3. noun
    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”
    synonyms: computer virus
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    type of:
    malevolent program, malware
    a computer program designed to have undesirable or harmful effects
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