Intimidation (also called cowing) is intentional behavior "which would cause a person of ordinary sensibilities" fear of injury or harm. It's not necessary to prove that the behavior was so violent as to cause terror or that the victim was actually frightened.
Criminal threatening (or threatening behavior) is the crime of intentionally or knowingly putting another person in fear of imminent bodily injury. "Threat of harm generally involves a perception of injury...physical or mental damage...act or instance of injury, or a material and detriment or loss to a person." "A terroristic threat is a crime generally involving a threat to commit violence communicated with the intent to terrorize another."
Threatening behaviours may be conceptualized as a maladaptive outgrowth of normal competitive urge for interrelational dominance generally seen in animals. Alternatively, intimidation may result from the type of society in which individuals are socialized, as human beings are generally reluctant to engage in confrontation or threaten violence.
Like all behavioral traits it exists in greater or lesser manifestation in each individual person over time, but may be a more significant "compensatory behavior" for some as opposed to others. Behavioral theorists often see threatening behaviours as a consequence of being threatened by others, including parents, authority figures, playmates and siblings. “Use of force is justified when a person reasonably believes that it is necessary for the defense of oneself or another against the immediate use of unlawful force.”
Intimidation may be employed consciously or unconsciously, and a percentage of people who employ it consciously may do so as the result of selfishly rationalized notions of its appropriation, utility or self-empowerment. Intimidation related to prejudice and discrimination may include conduct "which annoys, threatens, intimidates, alarms, or puts a person in fear of their safety...because of a belief or perception regarding such person's race, color, national origin, ancestry, gender, religion, religious practice, age, disability or sexual orientation, regardless of whether the belief or perception is correct."
Intimidation may be manifested in such manner as physical contacts, glowering countenance, emotional manipulation, verbal abuse, making someone feel lower than you, purposeful embarrassment and/or actual physical assault. “Behavior may include, but is not limited to, epithets, derogatory comments or slurs and lewd propositions, assault, impeding or blocking movement, offensive touching or any physical interference with normal work or movement, and visual insults, such as derogatory posters or cartoons.”
There is no legal definition in English law as to what behaviour constitutes "Intimidation", so it is up to the courts to decide on a case by case basis. However, if somebody threatens violence against somebody, then this may be a criminal offence.
Criminal threatening can be the result of verbal threats of violence, physical conduct (such as hand gestures or raised fists), actual physical contact, or even simply the placing of a sign, an object or graffiti on the property of another person with the purpose of coercing or terrorizing.
Criminal threatening is also defined by arson, vandalism, the delivery of noxious biological or chemical substances (or any substance that appears to be a toxic substance), or any other crime against the property of another person with the purpose of coercing or terrorizing any person in reckless disregard for causing fear, terror or inconvenience. Coercion is the use of “pressure, threats, or intimidation”  to compel or “force somebody to do something” or “make something to happen.”
"Terrorizing" generally means to cause alarm, fright, or dread in another person or inducing apprehension of violence from a hostile or threatening event, person or object. “It is not requisite, in order to constitute this crime, that personal violence should be committed.” 
- Domestic violence
- Intimidation of Parliament
- Psychological abuse
- Psychological trauma
- Witness intimidation
- Legal Definition of Intimidate 
- Threat of Harm Law & Legal Definition 
- Terroristic Threat Law & Legal Definition 
- Randall Collins, Violence: A Micro-sociological Theo323ry (2009)
- Legal Definition of Self-Defense 
- Harassment (Aggravated) Law & Legal Definition 
- Harassment Law & Legal Definition 
- Noose: ‘Shameful' sign makes ominous return, by Darryl Fears, Washington Post 
- "Coercion", Microsoft Encarta. Archived 2009-10-31.
- ""Compel" definition". Archived from the original on 2009-11-01. http://www.webcitation.org/5kyWYsntZ.
- Legal Definition of Terror, Terrorism 
- Ringer, Robert J. (2004). To Be or Not to Be Intimidated?: That Is the Question. M Evans & Co Inc. ISBN 1-59077-035-8.
- Just Fight On! Centre Against Workplace Bullying UK
- Coping.org - Eliminating Intimidation
- mobbing.ca (Mobbing resources in Canada)
- Together - Initimidation and Harassment