Which dictionary is that?The dictionary defines what words mean. Violence or threats of violence is an example of bullying. Calling someone harmless words is an example of teasing. They are not the same.
A group of children start to poke gentle fun at a classmate because he has red hair and they call him "carrot". The boy finds that funny and laughs. It's ok, they are his friends. His friends see that he's ok with "carrot" and it becomes his nickname. Teasing, but no harm done and no malicious intent. Not bullying.
Another group of kids see a boy with red hair and call him "carrot". The boy gets upset, and they think it's funny that he gets upset. It then becomes a game. So every time they see the boy, they call him "carrot" just to see his reaction. This is teasing with malicious intent. The kids can see that the boy is upset, and yet they continue, for their own amusement. This is bullying. I believe that this is what the OP is describing.
If you systematically continue with the teasing with the full knowledge of the emotional suffering you are causing, then it's bullying. Bullying doesn't just mean physical harm, it is also about emotional harm. Whether a person has the emotional maturity or a strategy to deal with the bullying or not doesn't detract from the fact that at that moment it's causing harm. Now, that person may indeed benefit from help to deal with the bullying, but to call the words "harmless" is wrong, as clearly right now they are doing harm.