Contagious or poisonous matter, as of specific ulcers, the bite of snakes, etc.; -- applied to organic poisons.
- Any of various simple submicroscopic parasites of plants, animals, and bacteria that often cause disease and that consist essentially of a core of RNA or DNA surrounded by a protein coat. Unable to replicate without a host cell, viruses are typically not considered living organisms.
- A disease caused by a virus.
- Something that poisons one's soul or mind: the pernicious virus of racism.
- Computer Science A computer virus.