1. To take an object out of storage after a period of disuse. Mothballs—little balls composed of a pungent chemical used to deter moths—are often kept in closets, attics, and other places where clothes are stored. Now that the weather is getting colder, it's time to bring our winter clothes out of mothballs. This new shipment of parts will allow us to bring the plane out of mothballs soon.

2. By extension, to begin to use or implement something. I did like your idea, Tom, but we can't bring it out of mothballs until we finish our outstanding projects.