pertaining to or involving the spreading of information and opinions about a product or service from person to person, especially on the Internet or in emails: a clever viral ad. See viral marketing.
becoming very popular by circulating quickly from person to person, especially through the Internet: the most memorable viral videos; This book is already viral two weeks before its official publication date.
pertaining to a computer virus.
go viral, to spread rapidly via the Internet, email, or other media: Footage of the candidate's off-color remarks went viral within minutes.