A computer virus that uses the macro capabilities of an application to execute code or programming steps that are embedded in data files associated with specific applications. Because users have learned not to execute programs from unknown sources for security reasons, attackers have turned to using macro viruses to embed malware in innocuous data files. Modern virus scanners detect macro viruses, as well.
A virus that is written in a macro language and placed within a document. Viruses have to be "run" in order to do things. When the document is opened and the macro is executed, commands in the macro language do the destruction or the prank. Thankfully, most viruses are harmless. Let's pray they stay that way! See Word macro virus, letter bomb, virus and macro.