The word "illicit" means something that is not allowed or prohibited by law, rules, or customs. It can refer to actions, behavior, or activities that are against the law or go against social norms and expectations. For example, drug use, gambling, or cheating on a test would all be considered illicit behaviors because they break established laws or rules. The word "illicit" is often used in contrast to "licit," which refers to actions that are allowed or permitted by law, customs, or social norms.