Bullying is a form of aggressive

Aggression

In psychology, as well as other social and behavioral sciences, aggression refers to behavior between members of the same species that is intended to cause humiliation, pain, or harm. Ferguson and Beaver defined aggressive behavior as "Behavior which is intended to increase the social dominance of...

 behavior

Behavior

Behavior or behaviour refers to the actions and mannerisms made by organisms, systems, or artificial entities in conjunction with its environment, which includes the other systems or organisms around as well as the physical environment...

 manifested by the use of force or coercion to affect others, particularly when the behavior is habitual and involves an imbalance of power. It can include verbal harassment

Harassment

Harassment covers a wide range of behaviors of an offensive nature. It is commonly understood as behaviour intended to disturb or upset, and it is characteristically repetitive. In the legal sense, it is intentional behaviour which is found threatening or disturbing...

, physical assault

Assault

In law, assault is a crime causing a victim to fear violence. The term is often confused with battery, which involves physical contact. The specific meaning of assault varies between countries, but can refer to an act that causes another to apprehend immediate and personal violence, or in the more...

 or coercion

Coercion

Coercion is the practice of forcing another party to behave in an involuntary manner by use of threats or intimidation or some other form of pressure or force. In law, coercion is codified as the duress crime. Such actions are used as leverage, to force the victim to act in the desired way...

 and may be directed repeatedly towards particular victims, perhaps on grounds of race

Race

Race is classification of humans into large and distinct populations or groups by factors such as heritable phenotypic characteristics or geographic ancestry, but also often influenced by and correlated with traits such as appearance, culture, ethnicity, and socio-economic status...

, religion

Religion

Religion is a collection of cultural systems, belief systems, and worldviews that establishes symbols that relate humanity to spirituality and, sometimes, to moral values. Many religions have narratives, symbols, traditions and sacred histories that are intended to give meaning to life or to...

, gender

Gender

Gender is a range of characteristics used to distinguish between males and females, particularly in the cases of men and women and the masculine and feminine attributes assigned to them. Depending on the context, the discriminating characteristics vary from sex to social role to gender identity...

, sexuality

Sexual orientation

Sexual orientation describes a pattern of emotional, romantic, or sexual attractions to the opposite sex, the same sex, both, or neither, and the genders that accompany them. By the convention of organized researchers, these attractions are subsumed under heterosexuality, homosexuality,...

, or ability.
The "imbalance of power" may be social power and/or physical power.