Bullying in general and at work specifically is an inherently vague term. It can mean any type of negative treatment – from simply ignoring and excluding a person from the activities that the rest of the workers are involved in to cruel jokes, personal attacks or even threats of physical violence or actual violence.
An employer does not have a legal obligation to prevent or remedy any type of unfair treatment or bullying, unless there is evidence that the reason for bad treatment is discriminatory, i.e. due to age, race, disability, sexual orientation, religion, or in retaliation for engaging in a specific protected activity. In other words, if your co-worker or a boss is yelling at you, or being rude or even insulting to you, that would not be unlawful unless there is evidence that the reasons for that bad treatment are discriminatory. The law does not protect workers from being treated badly. It only protects them from civil rights violations, specifically codified in the law.
If you believe you are a victim of bullying due to some type of personality conflict (and not due to discrimination), you should still consider bringing it to the attention of your higher ups or your HR department and ask them to intervene and help you. They may or may not be willing to help you. They may choose to talk to the alleged bully or even discipline him or her. It’s also not rare of management not to care about employees’ complaints of bullying and do little to nothing to address them. However, there is no legal way to force the employer to fix your work environment and stop the bullying to which you believe you have been subjected to.
If you suspect but are not sure that the reason you are treated badly at work is due to unlawful discrimination, you should discuss your legal and practical options with a knowledgeable attorney.