Learner's definition of FUR
1 [noncount] : the hairy coat of an animal especially when it is soft and thick 2 a : the fur of an animal used for clothing
[count]— often used before another noun b [count] : a piece of clothing (such as a coat) made with fur c [noncount] : a material that looks and feels like the fur of an animal
3 [noncount], British : a hard material that forms in metal pipes, boilers, etc.
◊ When (the) fur flies, someone becomes very angry or upset.