poison ivy (countable and uncountable, plural poison ivies)
- 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.
The name is often spelled "poison-ivy" to indicate that it is not a true ivy or Hedera.
- (ivy-like plant producing skin irritant): Toxicodendron orientale (Asian poison ivy), Toxicodendron radicans (eastern poison ivy), Toxicodendron rydbergii (western poison ivy)
- leaves of three, let it be
- poison oak
- poison sumac