sumach

1. Any of various shrubs or small trees of the genus Rhus and other genera in Anacardiaceae, particularly the elm-leaved sumac, Sicilian sumac, or tanner's sumac (Rhus coriaria).
2. Dried and chopped-up leaves and stems of a plant of the genus Rhus, particularly the tanner's sumac (see sense 1), used for dyeing and tanning leather or for medicinal purposes.
3. A sour spice popular in the Eastern Mediterranean, made from the berries of tanner's sumac.

verb

To apply a preparation of sumac to (an object), for example, to a piece of leather to tan it.