I'm sorry, it seems that there is a typo in your question. I believe you are asking for the medical definition of "diphenhydramine." Diphenhydramine is an antihistamine medication used to relieve symptoms of allergies, such as runny nose, sneezing, itching, and watery eyes. It works by blocking the effects of histamine, a substance in the body that causes allergic reactions. Diphenhydramine is also used for its sedative properties to treat insomnia and motion sickness, and to relieve symptoms of Parkinson's disease and relieve pain associated with inflammation of the lining of the mouth and throat. It can be taken orally, applied to the skin, or injected into a muscle. Common side effects include drowsiness, dry mouth, blurred vision, and dizziness.