1.nounRedundant use of words, a pleonasm, an unnecessary and tedious repetition.
"It is tautology to say, "Forward Planning"."
2.nounAn expression that features tautology.
3.nounIn propositional logic: a statement that is true for all truth values of its propositional variables. In first-order logic: a statement that is true for all truth values of its Boolean atoms.