In the legal sense of the term, to injure a person means to cause direct, or indirect, damage to a person or to that person's property. In other words, to legally injure somebody means that a person has caused harm to another person in such a way that they are entitled to legal compensation.
The definition of a legal injury spans over the entire field of the law. Any cause of action that a person is able to bring in a civil suit, or anything that a person is capable of being prosecuted for in a criminal court, is a result of the legal system seeing that action or non-action as an act punishable by law. A person can be held liable for injuring any part of a person from their physical body to their reputation.