Lawyer
Part of speech: noun
Definition: A professional person qualified (as by a law degree and/or bar exam) and authorized to practice law, i.e. conduct lawsuits and/or give legal advice. By extension, a legal layman who argues points of law.
Part of speech: verb
Definition: To practice law. To perform, or attempt to perform, the work of a lawyer. To make legalistic arguments. With "up", to acquire the services of a lawyer. With "up", to exercise the right to ask for the presence of one's attorney.
Prosecutor
Part of speech: noun
Definition: A lawyer who decides whether to charge a person with a crime and tries to prove in court that the person is guilty.