Lewis & Short

2. Lībĕrālis, e, adj., of or belonging to Liber or Bacchus: ludi, a festival in honor of Bacchus, = Liberalia (v. infra), Naev. ap. Paul. ex Fest. p. 116 Müll.
Hence, subst.: Lībĕrālĭa, ĭum, n., a festival in honor of Liber, celebrated on the 17th of March, the day on which youths received the manly toga, Ov. F. 3, 713: Liberalium dies, a pontificibus agonium martiale appellatur, Macr. S. 1, 4, § 15: sacra, id. ib. 1, 18, § 22; Calend. Maff. ap. Inscr. Orell. II. p. 411: Liberalia tu accusas, Cic. Att. 14, 10, 1: Liberalibus litteras accepi tuas, id. Fam. 12, 25, 1.
Called also: ludi Liberales: Liberalia Liberi festa, quae apud Graecos dicuntur Διονύσια. Libera lingua loquemur ludis Liberalibus, Naev. ap. Paul. ex Fest. p. 116 Müll.; Com. Rel. v. 113 Rib.