ˈspendˌthriftinessrare. [f. spendthrifty a. + -ness.] The act or quality of being spendthrifty. 1950H. J. Massingham Curious Traveller iv. 76 For such spendthriftiness no honest word can be said.1959Times 29 June 12/6 The feeling of pleasurable spend⁓thriftiness.