Undefeated means never having lost, especially in competition or battle. When a football team finishes the season undefeated, they've won every single game. When a boxer retires undefeated, no opponent ever beat them in the ring.

The word carries a sense of excellence and consistency. Going undefeated requires talent, preparation, focus, and sometimes a bit of luck. A chess player might stay undefeated through a tournament by winning some matches and drawing others (a draw doesn't count as a defeat). An undefeated debate team has never lost a competition.

You'll sometimes hear about undefeated streaks, where a team or athlete wins game after game without a loss. The 1972 Miami Dolphins remain the only undefeated team in NFL history to win the Super Bowl. These streaks become legendary precisely because they're so difficult to maintain.

People also use the word metaphorically. Someone facing a serious illness might call themselves undefeated, meaning their spirit remains strong despite challenges. The word suggests resilience: you can face tough opponents or difficult situations and still stand tall.