Bullying Free NZ have an excellent web resource which has information and support about bullying. 

https://www.bullyingfree.nz/about-bullying/what-is-bullying/

Below is some information from the website about what bullying is:

It’s easy to assume everyone knows what bullying is. But often the term bullying is used to describe other aggressive behaviour. This can make it hard for schools, parents and whānau, and the wider community to consistently identify and deal with bullying when it happens. Most widely-accepted definitions of bullying are based on four elements: bullying is deliberate, harmful, involves a power imbalance, and has an element of repetition.

Defining Bullying

Whether bullying is physical, verbal, or social (relational), four widely-accepted factors can be used to identify it:

• Bullying is deliberate - harming another person intentionally
• Bullying involves a misuse of power in a relationship
• Bullying is usually not a one-off - it is repeated, or has the potential to be repeated over time
• Bullying involves behaviour that can cause harm - it is not a normal part of growing up.

Bullying can happen anywhere, in person or online (cyberbullying), at any time, and can be verbal, physical or social (relational). It can be obvious or hidden.

Kids who bully use their power — such as physical strength, knowing something embarrassing, or popularity — to control or harm others. Bullying is when one student (or a group of students) keeps picking on another student again and again to make them feel bad. They say or do things to upset them, make fun of them, stop them from joining in, or keep hitting or punching them.