poison ivy

• Audio (General American):

  (file)

poison ivy (countable and uncountable, plural poison ivies)

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. (proscribed) Any species of Toxicodendron that can cause a rash, including poison oak and poison sumac.

• Asian poison ivy (Toxicodendron orientale)
• eastern poison ivy (Toxicodendron radicans)
• western poison ivy (Toxicodendron rydbergii)

• leaves of three, let it be
• poison oak (Toxicodendron diversilobum, Toxicodendron pubescens)
• poison sumac (Toxicodendron vernix)