Prune back is a gardening term that refers to the process of trimming or cutting away dead or overgrown branches from a plant. It is an important part of maintaining healthy plants and can help promote new growth. Trimming, which is the four letter solution to the crossword, is a key part of pruning back and involves cutting away excess branches and leaves. Pruning back can also involve removing diseased or damaged parts of the plant in order to prevent the spread of disease.