Source : Webster's Revised Unabridged Dictionary (1913)

Tonga \Ton"ga\, n. [Hind. t[=a]ng[=a], Skr. tama[.n]gaka.]
   A kind of light two-wheeled vehicle, usually for four
   persons, drawn by ponies or bullocks. [India]

Tonga \Ton"ga\, n. (Med.)
   A drug useful in neuralgia, derived from a Fijian plant
   supposed to be of the aroid genus {Epipremnum}.

Source : WordNet®

Tonga
     n 1: a monarchy on a Polynesian archipelago in the South Pacific;
          achieved independence from the United Kingdom in 1970
          [syn: {Kingdom of Tonga}, {Friendly Islands}]
     2: the language of the Tonga people of south central Africa
        (Zambia and Rhodesia)