Wool/wʊl/ Definition 1 of 5Pro Tip 1/3Animal Origin Remember that 'wool' in this sense refers to natural fiber, not synthetic material. The label says 100% wool, so it's not synthetic fleece. Pro Tip 2/3Common Use 'Wool' often implies the material is warm and used for winter clothing or blankets. You'll need a wool coat for the cold weather in December. Pro Tip 3/3Sustainable Fabric Wool is valued for being a sustainable and biodegradable fabric. Many prefer wool clothing because it's eco-friendly.