1. an inactive substance or a real medication that produces unpleasant or worsening symptoms in a patient or research participant because the person expects negative effects.
  2. a negative symptom experienced by a person with such expectations.

Origin of nocebo

1960–65; Latin nocēbō I shall be harmful; patterned after placebo Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018