1. in a way that spreads rapidly and widely through the internet or social media
Usage: informal; digital media
2. by means of a virus or in the manner of a viral infection
Usage: medical; biological

Examples

• The video spread virally across social media platforms.
• Her dance routine went virally popular overnight.
• The meme was shared virally by millions of users.
• The campaign was designed to spread virally through word of mouth.
• The infection spread virally through the population.
• The disease was transmitted virally from person to person.