Question

A word derived from a verb and used as an adjective is called a what as seen in the following example:

Gnarled and twisted, the old oak seemed like it would last forever.

Answer 1

It is called a participial adjective.

They are pretty common in English language and in the sentence provided the participial adjectives are "gnarled" and "twisted" as they were created from the verbs "to gnarl" and "to twist".