Multitudinal refers to something that is made up of a large number of people or things. One antonym for this word is "sparse," which refers to something that is thinly distributed or spread out. Another antonym is "few," meaning that something has a small number of people or things. "Singular," "solitary," and "individual" are additional antonyms for multitudinal. These words suggest that something or someone is unique, one-of-a-kind, or existing in isolation. Therefore, if you want to describe something that is not characterized by a large number of individuals, you can use any of the above antonyms for multitudinal.