1. [n]  the Turkic language spoken by the Tatar people living from the Volga to the Ural Mountains
2. [n]  a member of the Turkic-speaking people living from the Volga to the Ural Mountains (the name has been attributed to many other groups)
3. [n]  a member of the Mongolian people of central Asia who invaded Russia in the 13th century

TATAR is a 5 letter word that starts with T.