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