Unbounded means without limits or boundaries. When something is unbounded, it has no edges, no stopping point, no fence to contain it.

Think about the difference between a fenced yard and an open prairie. The yard has clear boundaries: walk far enough and you'll hit the fence. But on the prairie, you could walk in any direction for miles without running into a wall or barrier. The prairie feels unbounded.

In mathematics, an unbounded set of numbers goes on forever. The counting numbers (1, 2, 3, 4...) are unbounded because you can always add one more. No matter how high you count, there's always a bigger number waiting.

The word also describes feelings and qualities that seem limitless. A scientist might have unbounded curiosity, always wanting to learn more without ever feeling satisfied that she knows enough. An inventor might show unbounded creativity, coming up with idea after idea without running dry. When someone's enthusiasm is unbounded, their excitement seems endless.

The opposite of unbounded is bounded, meaning contained or limited. A soccer field is bounded by its lines. Your allowance is bounded by the amount your parents give you. But your imagination? That can be truly unbounded.