poison ivy

Short definition from Wiktionary

Noun

1. 1
   Any of three ivy-like species of Toxicodendron, known for their ability to cause an itching rash and blistering for most people, through urushiol, an oil that is a skin irritant.
2. 2
   Any species of Toxicodendron that can cause a rash, including poison oak and poison sumac.
3. 3
   A woody vine plant in the family Anacardiaceae (Toxicodendron radicans or Rhus toxicodendron), well-known for its ability to produce urushiol, a skin irritant that causes an itching rash for most people.