quan·ti·fi·er I. \ˈkwäntəˌfī(ə)r\noun (-s) 1.: a word (as a numeral) expressive of quantity < two, thirty, many, and much are quantifiers > 2.: a prefix that binds the variables in a logical formula by specifying their quantity — see existential operator, universal quantifier II. noun : one that quantifies ; especially : a person who quantifies data, an activity, or a field of study (as history)