Main Entry: poison oak

Function: noun

Date: 1743

1 : any of several plants related to poison ivy and producing an oil with similar irritating properties: as a : a bushy plant (Toxicodendron diversilobum syn. Rhus diversiloba) of the Pacific coast b : a bushy plant (Toxicodendron toxicarium syn. Rhus toxicodendron) chiefly of the southeastern U.S.
2 : poison ivy 1a