Define illness. illness synonyms, illness pronunciation, illness translation, English dictionary definition of illness. n. 1. a. Poor health resulting from disease of body or mind; sickness. b. A disease. 2. Obsolete a. The quality of being disagreeable or unpleasant. 3 meanings: 1. a disease or indisposition; sickness 2. a state of ill health 3. obsolete wickedness.... Click for more definitions. Learn the meaning, pronunciation and usage of the word illness, a noun for the state of being physically or mentally ill. Find out the difference between illness and disease, and see related words and collocations. Health encompasses physical, mental, and social well-being, not merely the absence of disease, as defined by the World Health Organization. Whereas, illness specifically refers to a state where there is a physical or mental disturbance involving symptoms and treatment.
