not allowed by the law 非法的；违法的 illicit drugs 违禁药物
not approved of by the normal rules of society 违背社会常规的；不正当的 an illicit love affair 不正当的风流韵事
Word Originearly 16th cent.: from French, or from Latin illicitus, from in- ‘not’ + licitus ‘allowed’, from the verb licere.