virus

noun vi·rus \ˈvī-rəs\

: an extremely small living thing that causes a disease and that spreads from one person or animal to another

: a disease or illness caused by a virus : a viral disease

computers : a program that is designed to harm a computer by deleting data, ruining files, etc., and that can be spread secretly from one computer to another

plural vi·rus·es

Full Definition of VIRUS

archaic : venom 1

a : the causative agent of an infectious disease

b : any of a large group of submicroscopic infective agents that are regarded either as extremely simple microorganisms or as 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, lower animals, or plants; also : filterable virus

c : a disease or illness caused by a virus

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

: 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 (as destroying data)

See virus defined for English-language learners

See virus defined for kids

Origin of VIRUS

Latin, venom, poisonous emanation; akin to Greek ios poison, Sanskrit viṣa; in senses 2 & 4, from New Latin, from Latin

First Known Use: 1599

Other Microbiology Terms

pathogen, salmonella, tetanus

Rhymes with VIRUS

Cyrus, gyrus, iris, Iris, Skyros

VIRUS Defined for Kids

virus

noun vi·rus \ˈvī-rəs\

Definition of VIRUS for Kids

: 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

: a disease caused by a virus

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

Medical Dictionary

virus

noun vi·rus \ˈvī-rəs\

Medical Definition of VIRUS

a : the causative agent of an infectious disease b : any of a large group of submicroscopic infective agents that are regarded either as extremely simple microorganisms or as 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, or plants; also : filterable virus c : a disease caused by a virus

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