The word "sub-division" refers to a part of a larger group or organization. Its antonyms are "union" or "conglomeration," which represent the idea of a larger group or organization. Another antonym for "sub-division" is "whole" or "entirety," which refers to a complete entity or object. "Integration" is another antonym, representing the union of diverse parts into a harmonious and consistent whole. "Unification" is an antonym meaning the process of combining two or more things into one. Finally, "aggregate" is an antonym that denotes the combined total of many different parts, without individualization or division.