The phrase "is out of sorts" refers to a person who is feeling irritable, unwell or in a bad mood. To describe the opposite of this phrase, one could use words such as cheerful, content, elated, pleased, or satisfied. These terms signify a positive mood or state of being. Additionally, a person who is feeling healthy or physically fit can also be seen as an antonym to "out of sorts." Other antonyms that can be used include confident, happy, energetic, and lively, which all entail a person who is in a good state of mind and body. Overall, the opposite of "is out of sorts" can be described as a well-being person with a positive state of mind.