1611 (implied in illicitous), from Fr. illicite (14c.), from L. illicitus "not allowed, unlawful, illegal," from in- "not" + licitus "lawful," pp. of licere "to be allowed."
Main Entry: il·lic·it Pronunciation: il-'li-s&t Function: adjective : not permitted :UNLAWFULillicit motive to defeat or evade the taxes —In re Haas, 48 Federal Reporter, Third Series 1153 (1995)>