"Bosom buddies" is a phrase that refers to extremely close friends or best friends. Antonyms for this term can include "enemies," "adversaries," or "opponents." These are individuals who are usually in opposition to one another and may have conflicting interests, goals, or beliefs. Another antonym could be "acquaintances" or "colleagues," which refer to individuals who are on friendly terms but not necessarily close friends. Alternatively, "strangers" or "unfamiliar individuals" could also be antonyms since they are individuals who have no prior relationship or connection. Ultimately, the antonym for "bosom buddies" would vary based on the context and the individuals involved.