Definition of ill

• an often persistent bodily disorder or disease; a cause for complaining
• (`ill is often used as a combining form) in a poor or improper or unsatisfactory manner; not well; "he was ill prepared"; "it ill befits a man to betray old friends"; "the car runs badly"; "he performed badly on the exam"; "the team played poorly"; "ill-fitting clothes"; "an ill-conceived plan"
• unfavorably or with disapproval; "tried not to speak ill of the dead"; "thought badly of him for his lack of concern"