Tautology n. : A repetition of the same meaning in different words; needless repetition of an idea in different words or phrases; a representation of anything as the cause, condition, or consequence of itself, as in the following lines: --//The dawn is overcast, the morning lowers,/And heavily in clouds brings on the day. Addison.

Example:
Can U falsify(prove false) a Tautology or a self-evident proposition(ie axiom)? What kind of propositions can?

Taxonomy
tautology, formula, valuation, sentence, propositional logic, propositional formula, propositional variables, logic, truth table, truth, first-order logic, Kleene, truth values, propositional variable, tautological, validities, negation, contradiction.

Defination from the web:
tautology (rhetoric). In propositional logic, a tautology (from the Greek word ταυτολογία) is a ... The word tautology was used by the ancient Greeks to describe a statement that was true merely by virtue of saying the same thing twice, a ...