shaggy hair (of an animal)
Refers to long, rough, or unkempt hair on animals, especially dogs. Often used in the phrase むく毛の犬 (shaggy-haired dog).
That dog has shaggy hair and is hard to brush.
Only when written 毳
Describes soft, fine, downy hair or fluff, such as on a chick or a peach. The kanji 毳 is specifically associated with this meaning, but it is very rare.
The chick's downy feathers are very soft.
産毛 refers specifically to the fine, soft hair on a newborn baby or the lanugo on a fetus, whereas むく毛 is used for animal hair or fluff.
Standard spelling for shaggy animal hair; the むく part is kana, 毛 is kanji.
Rare kanji spelling using 尨 (shaggy dog); mostly seen in older texts.
Single-character kanji for downy hair or fluff; very rare and literary.
The word むくげ is a compound of むく (possibly related to むくむく, an onomatopoeia for something fluffy or shaggy) and 毛 (hair). The exact origin of むく is uncertain.