(marketing) A video, image or text spread by "word of mouth" on the internet or by e-mail for humorous, political or marketing purposes.

(virology) Of or relating to a biological virus.

(virology) Caused by a virus.

(computing) Of the nature of an informatic virus; able to spread copies of itself to other computers.

(advertising and marketing) Spread by word of mouth, with minimal intervention in order to create buzz and interest.

(social media) Circulated rapidly and widely from one user to another.