Ill/ɪl/ Definition 1 of 4Pro Tip 1/3Severity Levels Use 'ill' to indicate varying severity of sickness, often modified by adverbs. He is slightly ill with a cold but still working. Pro Tip 2/3Short-term Sickness 'Ill' can imply a temporary condition, suggesting possible recovery. She's been ill but is expected to get better soon. Pro Tip 3/3Not Just Physical While often physical, 'ill' can also describe mental or emotional unwellness. His anxiety made him feel ill before the presentation.