Bullying refers to repetitively teasing, ridiculing, provoking, or tormenting others through various types of irritating, harassing, or aggressive actions, such as name-calling, threats, insults, and physical injury.
Other /More definition:
Bullying refers to a persistent pattern of behavior in which one person intentionally abuses another by means of verbal taunts or acts of teasing, physical assaults, deliberate exclusion from social activities, or attempts to sabotage his or her social relationships by spreading malicious gossip and rumors. Bullying is repetitively teasing, ridiculing, provoking, or tormenting others through various types of irritating, harassing, or aggressive actions, such as name-calling, threats, insults, and physical injury.

Moreover, Bullying is when one or more children expose another child, repeatedly and over time, to negative actions, such as physical contact, words, making faces or dirty gestures, and intentional exclusion from a group.
Other /More definition:
bullying means when one or more children expose another child, repeatedly and over time, to negative actions, such as physical contact, words, making faces or dirty gestures, and intentional exclusion from a group.