a compact mass of hair that forms in the stomach of cats, calves, etc, as a result of licking and swallowing the fur, and causes vomiting, coughing, bloat, weight loss, and depression
hairball in American English
(ˈhɛrˌbɔl)
noun
a rounded mass of hair that may form in the stomach or intestines of a cow, cat, or other animal that licks its coat