noun
glossy hair; glossy fur; glossy coat
Refers to the healthy shine or luster of hair, fur, or an animal's coat. Often used in positive descriptions of appearance.
彼女の毛艶の良い髪が印象的だった。
Her glossy hair was impressive.
この犬は毛艶が良くて、健康そうだ。
This dog has a glossy coat and looks healthy.
艶 alone means 'gloss' or 'luster' in general, while 毛艶 specifically refers to the glossiness of hair or fur.
Compound of 毛 (ke, 'hair') and 艶 (tsuya, 'gloss'). The reading けづや is a standard rendaku form.