Ton  n. 1 (in full long ton) unit of weight equal to 2,240 lb (1016.05 kg). 2 (in full short ton) unit of weight equal to 2,000 lb (907.19 kg). 3 = *metric ton. 4 (in full displacement ton) unit of measurement of a ship's weight or volume. 5 (usu. In pl.) Colloq. Large number or amount (tons of people). 6 slang a speed of 100 m.p.h. B £100.  weigh a ton colloq. Be very heavy. [originally the same word as *tun]