A verbal adjective is a form of a verb that functions as an adjective, describing a noun while retaining some characteristics of the verb. Verbal adjectives can express actions or states related to the noun they modify, and they often come in participial forms, like 'running' in 'the running water.' This term connects closely with verbal nouns and adverbs, as all three types derive from verbs and illustrate different ways in which actions can relate to other words in a sentence.