Entry 2 senses · 2 variants Webster, 1913 Celtic /(sĕlt"ĭk; kĕlt"ĭk)/ · Celt·ic · IPA /ˈkɛltɪk/ a. n. 01 a. Of or pertaining to the Celts; as, Celtic people, tribes, literature, tongue. 1. Of or pertaining to the Celts; as, Celtic people, tribes, literature, tongue. 02 n. The language of the Celts. 1. The language of the Celts.