A content word that can be used to refer to a person, place, thing, quality, or action WordNet 3.0 & Open English WordNet

Either a word that can be used to refer to a person, animal, place, thing, phenomenon, substance, quality or idea, or a word that modifies or describes a previous word or its referent; a substantive or adjective, sometimes also including other parts of speech such as numeral or pronoun. Wiktionary