/ ˈvaɪrəs; NAmE / noun
1.
a living thing, too small to be seen without a microscope , that causes infectious disease in people, animals and plants :
the flu virus
a virus infection
2.
( informal ) a disease caused by a virus :
There's a virus going around the office.
3.
instructions that are hidden within a computer program and are designed to cause faults or destroy data
—see also viral
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WORD ORIGIN
late Middle English (denoting the venom of a snake): from Latin , literally slimy liquid, poison . The earlier medical sense, superseded by the current use as a result of improved scientific understanding, was a substance produced in the body as the result of disease, especially one capable of infecting others .