Harassment refers to uncalled for words or types of conduct which tends to bother or abuse another person. Typical name-calling ("you are stupid" or " you are really a dummy") is a common form of harassment.
Duhaime Legal Dictionary
Unsolicited words or conduct which tend to annoy, alarm or abuse another person.
Words, such as threats, taunts or abusive language, and actions, such as offensive gestures, directed against a person which serve no legitimate purpose and tend to distress the listener.
The Free (Legal) Dictionary
the act of systematic and/or continued unwanted and annoying actions of one party or a group, including threats and demands. The purposes may vary, including racial prejudice, personal malice, an attempt to force someone to quit a job or grant sexual favors, apply illegal pressure to collect a bill, or merely gain sadistic pleasure from making someone fearful or anxious. Such activities may be the basis for a lawsuit if due to discrimination based on race or sex, a violation on the statutory limitations on collection agencies, involve revenge by an ex-spouse, or be shown to be a form of blackmail ("I'll stop bothering you, if you'll go to bed with me"). The victim may file a petition for a "stay away" (restraining) order, intended to prevent contact by the offensive party. A systematic pattern of harassment by an employee against another worker may subject the employer to a lawsuit for failure to protect the worker.
Harassment covers a wide range of offensive behaviour. It is commonly understood as behaviour intended to disturb or upset. In the legal sense, it is behaviour which is found threatening or disturbing.