A troll is an individual who uses telecommunications to annoy, harass, or intimidate someone maliciously or to incite fear.
Bullying and cyberbullying can be...
Spreading lies on social media
Following someone throughout the school to scare them
Making threatening remarks or sending repeated messages to annoy someone
First reflex in case of cyberbullying: the warning link!
By sending a warning, you send a clear message that you do not accept the behavior of the cyberbully and that you might decide to take further actions that could result in more severe consequences for them.