The phrase "on the outs" is a colloquial way of saying that two people or groups of people are no longer on good terms with one another. There are several synonyms for this phrase that may be more suitable depending on the context of the situation. Some possible alternatives include "at odds," "estranged," "in conflict," "disconnected," "separated," or "fallen out." Each of these terms has slightly different connotations, so it's important to choose the one that best describes the situation at hand. Regardless of the specific word choice, it's clear that when two parties are "on the outs," their relationship is not in a good place.