Undoubted means certain, unquestionable, or so clearly true that nobody doubts it. When something is undoubted, there's no room for disagreement or uncertainty about it.

If a scientist makes an undoubted discovery, the evidence is so strong that other scientists accept it as fact. When someone has undoubted talent at the piano, their skill is obvious to everyone who hears them play. The word describes things that are beyond question or dispute.

You might say that George Washington was the undoubted leader of the Continental Army, because nobody questioned his role or authority. Or that gravity is an undoubted force in our universe, since we can observe and measure its effects everywhere.

It's stronger than just saying something is “probably true” or “likely.” When something is undoubted, it's settled, established, and accepted as real or true.

Notice that undoubted describes the thing itself, not people's opinions about it. An undoubted fact remains true whether people believe it or not, though undoubted things are so clearly true that everyone does believe them.