Licentious describes a person, a life, or a story that is sexually wild and does not keep the usual moral rules — uncontrolled, often in a way other people judge as shameful. It is a formal, slightly old-fashioned adjective. You will meet it in novels, in moral writing, and in news that wants a strong, bookish word; you will not hear it much in the shop. Everyday English is more likely to say sleeping around, wild, or immoral, depending on how blunt the speaker wants to be. It comes from Latin for “full of licence,” licence here meaning freedom. Though actually that freedom is the dark twin of a driving licence: not permission on paper, but “I may do as I like.” A sentence that uses licentious to mean “having a licence” has taken the wrong road. There is a rarer, still bookish stretch in which it means “too free with the rules” in language or law, but the sexual, moral sense is the one students will actually read.