Antonyms for the phrase "are uptight" can include words such as relaxed, calm, easy-going, carefree, mellow, chilled, and laid-back. When someone is described as uptight, it generally means they are anxious, tense, or overly serious. Therefore, using an antonym can help to communicate the idea that someone is relaxed, cheerful, or easy to be around. Additionally, using antonyms can help to convey a more positive tone in communication. For instance, one might say, "I appreciate how relaxed and laid-back you are," instead of saying, "You need to loosen up and stop being so uptight.