1. n. (pathology) An abnormal condition of a human, animal or plant that causes discomfort or dysfunction; distinct from injury insofar as the latter is usually instantaneously acquired.
The tomato plants had some kind of disease that left their leaves splotchy and fruit withered.
2. n. (by extension) Any abnormal or harmful condition, as of society, people's attitudes, way of living etc.
3. n. Lack of ease; uneasiness; trouble; vexation; disquiet.
4. v. (obsolete) To cause unease; to annoy, irritate.