Cojoin means to join or unite two or more things together. The antonyms of cojoin include separate, divide, isolate, detach, disconnect, disjoin, and sever. These words mean to undo something that has been joined or united. Separating means to divide something into different parts, whereas dividing means to split something into smaller parts. Isolating means to keep something away from others, while detaching means to remove something from a larger group. Disconnecting means to break a connection, whereas disjoining and severing both mean to separate something completely. All of these words are opposite in meaning to cojoin and signify separation or disunity.