It doesn't always have to be a crowd, even a few onlookers in a hall can discourage a bully by standing up for victim of bullying. The child should avoid being alone if they are dealing with a bully as there would be no one else to discourage it. Bullying obviously shouldn't be tolerated in the school system, but this misses the point. The point was whether or not trolling is cyberbullying, and their definitions suggest that they are not.
I would like to ask a question though just to see if you are misunderstanding one of the solutions. What do you think the parent would do (assuming that they care) if they find out that their child is being bullied?