To prune means to clip, crop, cut back, and weed out. Pruning usually happens to overgrown trees and bushes, but can also be helpful for wild eyebrows and guest lists that are too long.
You may have also heard of another form of prune: the kind you eat. But other than dried plums, the word is generally used in verb form to describe giving something a much needed trim. Gardeners prune plants, cutting back dead branches and weak parts so they can thrive and grow better. Companies prune budgets to cut back on unnecessary spending. And you might need to prune your baseball hat collection if you're running out of places to put them.