"Matted hair" refers to hair that is tangled and clumped together, usually creating knots or mats that are difficult to comb or brush through. Full definition
A cyst or thick capsule is created under the skin as the larva grows; a circular breathing hole may appear as an open wound with matted hair around it. (cathealth.com)
''... Mark her bold manner, impudent stare, fine figure, and the roll of matted hair lying as an ensign of her trade upon her proud head. (religion-online.org)
Some dog brushes are used to remove matted hair while some are used to reduce shedding. (crittersitca.com)