A cocoon is a protective silk covering that certain insects spin around themselves while they transform from one life stage to another. When a caterpillar is ready to become a moth, it wraps itself in a cocoon made of silk threads from its own body. Inside this safe shelter, the caterpillar's body completely reorganizes itself, a process called metamorphosis. The cocoon helps keep the transforming insect safe from predators, weather, and injury during this vulnerable time.

The most famous cocoon-makers are silkworms, whose cocoons humans have harvested for thousands of years to make silk fabric. A single silkworm cocoon contains about 1,000 yards of silk thread.

People also use cocoon as a verb meaning to wrap yourself up for comfort and protection. You might cocoon yourself in blankets on a cold morning, or cocoon yourself in your room with a good book when you want quiet time. When someone complains about being cocooned from the real world, they mean being overly protected or sheltered from challenges and experiences that help people grow.