To unfurl means to unroll or spread out something that was tightly wrapped or folded, like opening a scroll or letting a flag spread out in the wind. When a ship's crew unfurls the sails, they release them from their bound position so they can catch the wind and pull the ship forward. When you unfurl a rolled-up poster, you're opening it flat so you can see the whole picture.

The word carries a sense of something blossoming or revealing itself. A butterfly unfurls its wings after emerging from its chrysalis, slowly spreading them for the first time. A fern frond unfurls as it grows, uncurling from a tight spiral into a graceful leaf.

You'll often see unfurl used for flags, banners, and sails because these objects start compact and then open dramatically. When people unfurl a banner at a rally, they're letting it drop open so everyone can read their message. The opposite of unfurl is furl, which means to roll or fold something back up tightly.