To furl means to roll or wrap something up tightly and securely, usually a flag, sail, or piece of fabric. When a ship's crew furls the sails, they bundle them up and tie them to the mast so they won't catch the wind. When a color guard furls the flag at the end of a ceremony, they carefully roll it into a compact bundle.

The opposite of furl is unfurl, which means to unroll or spread something out. You might watch a flag unfurl in the breeze as someone raises it up a flagpole, or see a ship's crew unfurl their sails when they're ready to catch the wind and start moving.

In a storm, sailors had to furl the sails quickly to keep the ship safe. Today, you might see flags furled when they're being stored or carried, like when military honor guards furl flags during formal ceremonies. Some awnings and umbrellas are designed to furl automatically, rolling up neatly when you press a button.