Being ill with is a phrase used to describe being sick or unwell. Some possible antonyms for this phrase include healthy, well, and fit. These words all suggest a state of good physical or mental health, and are the opposite of being ill with. Other antonyms for this phrase may include robust, strong, and vigorous. These words all imply a sense of vitality and energy, which is the opposite of feeling sick or weak. While being ill with can be a challenging and uncomfortable experience, there are many antonyms that can help to describe a state of good health and well-being.