/ ˌpəʊstˈmɒdɪfaɪə(r); NAmE ˌpoʊstˈmɑːd-/ noun
( grammar ) a word, such as an adjective or adverb, that describes another word or group of words, or restricts its/their meaning in some way, and is placed after it/them :
In 'run fast', the adverb 'fast' is a postmodifier.
—compare modifier , premodifier