Mammoth Uncensored Word List:
15 - 19 letter words starting with t

tectonostratigraphy tenderheartednesses territorializations tetrafluoroethylene thermoelectricities thermoluminescences thermoperiodicities transformationalist transmogrifications transplantabilities transubstantiations trestrigintillionth tresvigintillionths tridimensionalities trigintacentillions