pp. Using online media and technologies to attack or gang up on a person.
2014
The background against which the inquiry took place was an increasing number of situations in which people were committing criminal offences using social networks — particularly Facebook and Twitter. The committee examined instances of cyber bullying, revenge porn, trolling and virtual mobbing to try and determine whether or not they were criminal offences and if they were, whether new legislation was required to deal with them.
2014
He uses his book to describe how one can die by Twitter. He calls his experience a virtual mobbing.
2011 (earliest)
The synonym cybermobbing (or cyber-mobbing) dates to at least 2009 and is likely a few years older than that.