The definition of the Fujita scale is a scale for measuring the wind speed of a tornado and its potential for destruction with F0 meaning wind speeds of 40-72 mph up to F6 which is wind speeds up to 319 to 380 mph.
(noun)An example of the Fujita scale is what a tornado expert would use to determine the damage a tornado could do if it sets down on a town.
See Fujita scale in Webster's New World College Dictionary
Origin: after T. T. Fujita (1920-98), U.S. meteorologist who devised it