1. needless repetition of an idea, statement, or word
  2. an expression or phrase that says the same thing twice, just in a different way. 

Actual example of tautology:

  • A less abstract example of tautology is saying, “The ball is green or the ball is not green.”

Examples of tautology in a sentence:

  • The politician’s advertisement was simply tautology he restated several times within a thirty second period.
  • The teacher explained the tautology in the “the dead corpse” by reminding students that a corpse is already dead