To uncurl means to straighten or unroll something that was curved or coiled up. When a cat uncurls from its sleeping position, it stretches out from the tight ball it was curled into. When you uncurl your fingers from a fist, you open your hand and extend your digits.

Think of a fern's new leaves in spring: they start tightly curled like tiny scrolls, then gradually uncurl as they grow, unfurling into their full, spread-out shape. A sleeping child might uncurl their body in the morning, going from a tucked position to a stretched-out one. You might uncurl a ribbon that's been wound around a package, or watch a rolled-up piece of paper slowly uncurl when you let it go.

The word suggests a gentle, gradual motion rather than a sudden snap. When something uncurls, it's releasing tension and returning to a more relaxed, open state. A tense person might uncurl their clenched toes, or a snake might uncurl from its coiled resting position to slither away.