Homophones: ton, tun; Rhymes: -ʌn (General Australian) tŏn, IPA : /tɒn/ (especially when emphasizing tonnes and not tons) Rhymes: -ɒn; Noun . tonne (plural tonnes) A metric unit of mass equal to 1000 kilograms. Symbol: t (colloquial, darts) A score of 100. Usage notes . A tonne (about 2204.6 pounds) is not exactly the same as a long ton (2240 pounds).