- 1 [uncountable] illness; bad health She's been away from work because of sickness. insurance against sickness and unemployment
- 2 [uncountable, countable, usually singular] a particular type of illness or disease altitude/radiation sickness a sickness common in the tropics see also sleeping sickness
- 3 [uncountable] the feeling that you are likely to vomit (= bring food back up from the stomach to the mouth); the fact of vomiting synonym nausea car sickness (= the feeling of sickness that some people get when traveling in a car) see also morning sickness, motion sickness
- 4[singular] a feeling of great sadness, disappointment, or disgust He felt a sickness rise in him at the thought of leaving.