The meaning of VIRAL is of, relating to, or caused by a virus. How to use viral in a sentence. Viral infections are any illness you get from a virus (a small germ that uses your cells to reproduce). Examples include the flu, colds, COVID-19 and HPV. viral adjective (INTERNET) used to describe something that quickly becomes very popular or well known by being published on the internet or sent from person to person by email, phone, etc.: The word Viral means "relating to viruses " (small infectious agents). It may also refer to: Memetic behavior likened that of a virus, for example: 1. Of, relating to, or caused by a virus. 2. Of or relating to the rapid propagation of information, ideas, or trends by means of social networks rather than conventional mass media: viral marketing. A viral film clip, story, or message is one that spreads quickly because people share it on social media and send it to each other. Her tweet went viral, leading to widespread discussions online. The term commonly refers to something that spreads rapidly and widely, especially in relation to internet content or trends.