The term 'thick-skinned fruit' refers to two fruits in particular: the UGLI and the POMELO. The UGLI is a citrus fruit that is a hybrid of grapefruit, tangerine, and orange. It has a thick, bumpy skin and a tart flavor. The POMELO is a large citrus fruit that is related to the grapefruit. It has a thick, yellow-green skin and a sweet-tart flavor. Both of these fruits are popular in many parts of the world and are often used in salads, desserts, and other dishes.