Grayanotoxin (also known as mad honey disease): n.
A neurotoxin found in the nectar of certain species of rhododendron (Rhododendron spp.) and laurel (Kalmia spp.) and in unprocessed foods produced from the nectar, such as unpasteurized honey, and causing temporary effects such as nausea, vomiting, dizziness, and irregular heartbeat if ingested.