An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

A segment of self-replicating code planted illegally in a computer program, often to damage or shut down a system or network (Dictionary.com).

→ computer; → virus.

1) 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 (Dictionary.com).
2) → computer virus.

From L. virus "poison, sap of plants, slimy liquid, a potent juice," ultimately from PIE *ueis- "fluidity, slime, poison;" cf. Pers. bīš "a poisonous plant;" Mid.Pers. wiš "poison;" Av. viš-, viša- "poison;" Skt. visa- "venom, poison, poisonous;" L. viscum "sticky substance, birdlime;" Gk. ios "poison," ixos "mistletoe, birdlime;" O.C.S. višnja "cherry;" O.Irish fi "poison;" Welsh gwy "poison."