Entry 3 senses · 2 variants Webster, 1913 Thai /(tī)/ · IPA /taɪ/ n. a. 01 n. The language of Thailand (Siam); it is a member of the Tai group of languages. 1. The language of Thailand (Siam); it is a member of the Tai group of languages. 02 a. Of or pertaining to the Thai language, a member of the Tai group of languages. 1. Of or pertaining to the Thai language, a member of the Tai group of languages. 2. Of or pertaining to Thailand or its people.