1. expressing the same thing twice in different words; redundant
Usage: formal; logic and rhetoric
2. being a logical tautology; always true by definition
Usage: logic and philosophy

Examples

• The phrase ‘free gift’ is tautologous since all gifts are free by definition.
• His tautologous explanation added no new information to the discussion.
• The statement ‘either it will rain or it will not rain’ is tautologous.
• She avoided tautologous expressions in her writing to keep it concise.
• The professor pointed out that the argument was tautologous and circular.
• In logic, tautologous statements are always true regardless of circumstances.