1. In some classifications: comprising those members of the genus Rhus having foliage that is poisonous to the touch; of North America and northern South America.
2. An alternative genus for six species of poison ivies and poison oaks within the genus Rhus.
3. A genus (formerly rhus) of shrubs, vines, or trees that yields a highly allergenic oleoresin which causes a severe contact dermatitis.

The most toxic species are toxicodendron vernix (poison sumac), toxicodendron Diversilobum (poison oak), and toxicodendron Radicans (poison ivy). Toxicodendron Vernicifera yields a useful varnish from which certain enzymes (laccases) are obtained.