The term 'prickly tree' is a reference to a type of tree that has thorns or spines on its branches and leaves. The crossword solution for this term is 'THORN, ' which is a five-letter word. Thorns are sharp, pointed structures that grow on the stems and branches of certain plants, such as roses, blackberries, and cacti. They are used to protect the plant from predators and to discourage animals from eating the plant's leaves and fruits. Prickly trees are often found in dry, arid climates, where they provide shelter and food for wildlife.