LithuanianPronunciation: /lɪθjʊˈeɪnɪən, lɪθʊ-/Translate Lithuanian | into Italian | into Spanish Definition of Lithuanian adjective relating to Lithuania or its people or language. noun 1a native or citizen of Lithuania, or a person of Lithuanian descent. 2 [mass noun] the language of Lithuania, which belongs to the Baltic branch of the Indo-European family and has about 3.5 million speakers. Lithuanian in other Oxford dictionaries Definition of Lithuanian in the US English dictionary