The Free On-line Dictionary of Computing (30 December 2018):

tautological set

    A notion introduced by Florentin Smarandache: An
   element x(T, I, F) belongs more than sure to the set M; here
   T, I, F are real subsets representing the truth,
   indeterminacy, and falsity percentages respectively, and
   sup(T)>100.

   tautological set are used for universally true propositions
   where no parameter such as time, space, or subjectivity
   influences the truth value.

   [Florentin Smarandache, "A Unifying Field in Logics. /
   Neutrosophy: Neutrosophic Probability, Set, and
   Logic", American Research Press, Rehoboth, 1999
   (http://gallup.unm.edu/~smarandache/neut-ad.htm)]

   (1999-11-24)