To debilitate means to make someone or something much weaker or less able to function normally. When an illness debilitates a person, it drains their strength and energy, making everyday activities difficult or impossible. A debilitating injury might keep an athlete off the field for months, or a debilitating migraine might force someone to stay in a dark, quiet room until it passes.

The word suggests serious weakness that goes beyond mild tiredness. You might feel tired after a long day at school, but a debilitating illness could leave you too weak to get out of bed. A drought might debilitate crops, causing them to wither instead of grow. Fear can debilitate an army, sapping its courage before a battle even begins.

Something debilitating significantly reduces your ability to do what you normally could, creating major limitations in your life. A broken pencil is annoying, but a broken leg is debilitating because it affects so much of what you can do. When doctors help patients recover from debilitating conditions, they're helping restore the strength and ability that the illness or injury took away.