1.(logic) a statement that is necessarily true - the statement 'he is brave or he is not brave' is a tautology • Derivationally related forms: tautological • Topics: logic • Hypernyms: truth, true statement 2. useless repetition - to say that something is 'adequate enough' is a tautology • Derivationally related forms: tautologic, tautological • Hypernyms: repetitiveness, repetitiousness