The term "dead coat" is not a commonly used phrase, but it can refer to an old or outdated coat that has lost its original color and vibrancy. Full definition
They also require stripping to remove their old dead coat twice yearly. (puppiesndogs.com)
Regular brushing stimulates circulation, removes dead skin cells, distributes natural oils and gets dead coat off the pet before it can get all over the house. (petbusiness.com)
Shedding happens a couple of times a year, and a hound glove really helps in removing dead coat. (en.wikipedia.org)