Cohabitees are common these days, as more and more couples decide to live together without getting married. If you're searching for a synonym for "cohabiter," you might try "roommate," "live-in partner," "domestic partner," or "significant other." These terms all describe someone who shares a residence with another person but is not necessarily married to them. Each of these synonyms has a slightly different connotation, so choose the one that best fits your situation. Whatever word you use, remember that the most important thing is the quality of your relationship, not the label you give it.