[ vahy-ruh s ]
/ ˈvaɪ rəs /

noun, plural vi·rus·es.

an ultramicroscopic (20 to 300 nm in diameter), metabolically inert, infectious agent that replicates only within the cells of living hosts, mainly bacteria, plants, and animals: composed of an RNA or DNA core, a protein coat, and, in more complex types, a surrounding envelope.
Informal. a viral disease.
a corrupting influence on morals or the intellect; poison.
a segment of self-replicating code planted illegally in a computer program, often to damage or shut down a system or network.



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Origin of virus

1590–1600; < Latin vīrus slime, poison; akin to ooze2


vi·rus·like, adjectivean·ti·vi·rus, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

Example sentences from the Web for antivirus

  • Basically, the malware presents itself as a piece of antivirus software that is going to protect your machine.

    Is Your Mac Safe?|Dan Lyons|June 21, 2011|DAILY BEAST
  • And most users don't need to install things like antivirus software that's almost a necessity on Windows.

    Is Your Mac Safe?|Dan Lyons|June 21, 2011|DAILY BEAST

British Dictionary definitions for antivirus (1 of 2)

/ (ˈæntɪˌvaɪrəs) /


(modifier) a piece of software designed to prevent viruses entering a computer system or networkantivirus software
(modifier) of or relating to such a piece of software

British Dictionary definitions for antivirus (2 of 2)

/ (ˈvaɪrəs) /

noun plural -ruses

any of a group of submicroscopic entities consisting of a single nucleic acid chain surrounded by a protein coat and capable of replication only within the cells of living organisms: many are pathogenic
informal a disease caused by a virus
any corrupting or infecting influence
computing an unauthorized program that inserts itself into a computer system and then propagates itself to other computers via networks or disks; when activated it interferes with the operation of the computer

Derived forms of virus

virus-like, adjective

Word Origin for virus

C16: from Latin: slime, poisonous liquid; related to Old English wāse marsh, Greek ios poison
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medical definitions for antivirus

[ vīrəs ]

n. pl. vi•rus•es

Any of a large group of submicroscopic agents that act as parasites and consist of a segment of DNA or RNA surrounded by a coat of protein. Because viruses are unable to replicate without a host cell, they are not considered living organisms in conventional taxonomic systems. Nonetheless, they are described as “live” when they are capable of replicating and causing disease.
A disease caused by a virus.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Scientific definitions for antivirus

[ vīrəs ]

Plural viruses

Any of various extremely small, often disease-causing agents consisting of a particle (the virion), containing a segment of RNA or DNA within a protein coat known as a capsid. Viruses are not technically considered living organisms because they are devoid of biological processes (such as metabolism and respiration) and cannot reproduce on their own but require a living cell (of a plant, animal, or bacterium) to make more viruses. Viruses reproduce first either by injecting their genetic material into the host cell or by fully entering the cell and shedding their protein coat. The genetic material may then be incorporated into the cell's own genome or remain in the cytoplasm. Eventually the viral genes instruct the cell to produce new viruses, which often cause the cell to die upon their exit. Rather than being primordial forms of life, viruses probably evolved from rogue pieces of cellular nucleic acids. The common cold, influenza, chickenpox, smallpox, measles, mumps, yellow fever, hemorrhagic fevers, and some cancers are among the diseases caused by viruses.
Computer Science A computer program that duplicates itself in a manner that is harmful to normal computer use. Most viruses work by attaching themselves to another program. The amount of damage varies; viruses may erase all data or do nothing but reproduce themselves.

Other words from virus

viral adjective
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Cultural definitions for antivirus (1 of 3)

[ (veye-ruhs) ]

plur. viruses

Microorganisms consisting of DNA and RNA molecules wrapped in a protective coating of proteins. Viruses are the most primitive form of life. They depend on other living cells for their reproduction and growth. (See under “Medicine and Health.”)

notes for virus

Viruses cause many diseases. (See viral infection.)

Cultural definitions for antivirus (2 of 3)

[ (veye-ruhs) ]

plur. viruses

A minute organism that consists of a core of nucleic acid surrounded by protein. Viruses, which are so small that a special kind of microscope is needed to view them, can grow and reproduce only inside living cells. (See under “Life Sciences.”)

Cultural definitions for antivirus (3 of 3)


See computer virus.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.