An indictment is a formal accusation of a crime made against a person by a grand jury. [Grand jury: a group of citizens who decide if there is enough evidence to bring someone to trial]. The indictment outlines the charges against the person and marks the beginning of a criminal trial. For example, a grand jury may issue an indictment against someone for robbery.
Very Simple Definition:
An indictment is a formal charge of a crime. It means someone is accused of doing something wrong. For example, if the police think someone has stolen something, they may charge them with theft. That is an indictment.