mad-dog

Adjective

 * 1) Fanatically or irrationally ferocious.

Usage notes
It can be difficult to distinguish between the standard practice of inserting a hyphen into a noun phrase when it is used attributively (that is, using mad-dog for the noun phrase mad dog) and the use of this term as a genuine adjective. There is evidence that this form is sometimes used as a genuine adjective, as can be seen in the quotations. However, the most common usage is as an attributive noun.