Dan Olweus provides this definition of bullying:
"A person is bullied when he or she is exposed, repeatedly and over time, to negative actions on the part of one or more other persons, and he or she has difficulty defending himself or herself." - from "Bullying at School: What We Know and What We Can Do" Malden, Massachusetts: Blackwell Publishers Inc.
Dear Colleague Letter written to advise on harassing behaviors and civil rights law by the US Department of Education, Office of Civil Rights:
“Harassing conduct may take many forms, including verbal acts and name-calling; graphic and written statements, which may include use of cell phones or the Internet; or other conduct that may be physically threatening, harmful, or humiliating. Harassment does not have to include intent to harm, be directed at a specific target, or involve repeated incidents. Harassment creates a hostile environment when the conduct is sufficiently severe, pervasive, or persistent so as to interfere with or limit a student’s ability to participate in or benefit from the services, activities, or opportunities offered by a school. When such harassment is based on race, color, national origin, sex, or disability, it violates the civil rights laws that OCR enforces.” - link
The World Health Organization provides this definition of bullying:
“Bullying is a multifaceted form of mistreatment, mostly seen in schools and the workplace. It is characterized by the repeated exposure of one person to physical and/or emotional aggression including teasing, name calling, mockery, threats, harassment, taunting, hazing, social exclusion or rumors.” - link
The Swedish Council for Crime Prevention in their 2008 publication Effectiveness of Programmes to Reduce School Bullying reports:
“The definition of school bullying includes several key elements: physical, verbal, or psychological attack or intimidation that is intended to cause fear, distress, or harm to the victim; an imbalance of power (psychological or physical), with a more powerful child (or children) oppressing less powerful ones; and repeated incidents between the same children over a prolonged period. School bullying can occur in school or on the way to or from school. It is not bullying when two persons of the same strength (physical, psychological, or verbal) victimize each other.” - link
U.S. Department of Justice, Office of Community Oriented Policing Services in their publication: Problem-Oriented Guides for Police Problem-Specific Guides Series No. 12: Bullying in Schools defines bullying:
"Bullying has two key components: repeated harmful acts and an imbalance of power. It involves repeated physical, verbal, or psychological attacks or intimidation directed against a victim who cannot properly defend him- or herself because of size or strength, or because the victim is outnumbered or less psychologically resilient.
Bullying includes assault, tripping, intimidation, rumor-spreading and isolation, demands for money, destruction of property, theft of valued possessions, destruction of another’s work, and name-calling.
In the United States, several other school behaviors (some of which are illegal) are recognized as forms of bullying, such as:
• Sexual harassment (e.g., Repeated exhibitionism, voyeurism, sexual propositioning, and sexual abuse involving unwanted physical contact)
• Ostracism based on perceived sexual orientation
• Hazing (e.g., Upper-level high school athletes’ imposing painfully embarrassing initiation rituals on their new freshmen teammates).
Not all taunting, teasing and fighting among schoolchildren constitutes bullying.“Two persons of approximately the same strength (physical or psychological)…fighting or quarreling” is not bullying. Rather, bullying entails repeated acts by someone perceived as physically or psychologically more powerful." - link