Definition of adjective noun in Oxford Advanced Learner's Dictionary . Meaning, pronunciation, picture, example sentences, grammar, usage notes, synonyms and more. What Is an Adjective ? An adjective is a part of speech that can be used to describe or provide more information about a noun or pronoun that acts as the subject in a sentence. Adjectives are found after the verb or before the noun it modifies. Definition of an Adjective In other words, we can say that a noun or pronoun that serves as the subject of a sentence can be described or given additional information using an adjective . Adjectives are found before the noun they modify as well as after the verb they modify. ADJECTIVE definition : 1. a word that describes a noun or pronoun: 2. a word that describes a noun or pronoun: 3. a word…. Learn more.