virus

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noun vi·rus \ˈvī-rəs\

Definition of virus

plural

viruses

  1. 1a :  any of a large group of submicroscopic infective agents that are usually regarded as nonliving extremely complex molecules, that typically contain a protein coat surrounding an RNA or DNA core of genetic material but no semipermeable membrane, that are capable of growth and multiplication only in living cells, and that cause various important diseases in humans, animals, and plants; also :  filterable virusb :  a disease or illness caused by a virusc :  the causative agent of an infectious disease

  2. 2 :  something that poisons the mind or soul the force of this virus of prejudice — V. S. Waters

  3. 3 :  a computer program that is usually hidden within another seemingly innocuous program and that produces copies of itself and inserts them into other programs and usually performs a malicious action (such as destroying data)

  4. 4 archaic :  venom 1

Examples of virus in a Sentence

  1. Is the illness caused by bacteria or a virus?

  2. I think I have the virus that's going around this winter.

  3. The software checks your hard drive for viruses.

Recent Examples of virus from the Web

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'virus.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Origin and Etymology of virus

Latin, venom, poisonous emanation; akin to Greek ios poison, Sanskrit viṣa; in senses 1 & 3, from New Latin, from Latin

Other Microbiology Terms


VIRUS Defined for Kids

virus

play
noun vi·rus \ˈvī-rəs\

Definition of virus for Students

  1. 1 :  a disease-causing agent that is too tiny to be seen by the ordinary microscope, that may be a living organism or may be a very special kind of protein molecule, and that can only multiply when inside the cell of an organism

  2. 2 :  a disease caused by a virus

  3. 3 :  a usually hidden computer program that causes harm by making copies of itself and inserting them into other programs


Medical Dictionary

virus

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noun vi·rus \ˈvī-rəs\

Medical Definition of virus

  1. 1a:  the causative agent of an infectious diseaseb:  any of a large group of submicroscopic, infective agents that are usually regarded as nonliving, extremely complex molecules or sometimes as very simple microorganisms, that typically contain a protein coat surrounding an RNA or DNA core of genetic material but no semipermeable membrane, that are capable of growth and multiplication only in living cells, and that cause various important diseases in humans, animals, and plants; also :  filterable virusc:  a disease caused by a virus

  2. 2:  an antigenic but not infective material (as vaccine lymph) obtainable from a case of an infectious disease



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