sumac

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various shrubs or small trees of the genera Rhus and Toxicodendron, having compound leaves, clusters of small greenish flowers, and usually red, hairy fruit. Species in the genus Toxicodendron, such as poison sumac, have toxic sap.
• noun A tart, dark reddish-brown powder made from the ground dried fruits of a Eurasian sumac (Rhus coriaria), used as a seasoning in Middle Eastern cuisine.

from The Century Dictionary.

• In leather manufacturing, to treat with sumac.
• noun One of numerous shrubs or small trees of the genus Rhus. See def. 2, and phrases below.
• noun A product of the dried and ground leaves of certain shrubs or trees of the genus Rhus or of other genera, much used for tanning light-colored leathers and to some extent for dyeing.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Bot.) Any plant of the genus Rhus, shrubs or small trees with usually compound leaves and clusters of small flowers. Some of the species are used in tanning, some in dyeing, and some in medicine. One, the Japanese Rhus vernicifera, yields the celebrated Japan varnish, or lacquer.
• noun The powdered leaves, peduncles, and young branches of certain species of the sumac plant, used in tanning and dyeing.
• noun (Bot.) See under Poison.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Any of various shrubs or small trees of the genus Rhus including the poison ivy and poison oak.
• noun A sour spice popular in the Eastern Mediterranean made from the berries of the plant.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun wood of a sumac
• noun a shrub or tree of the genus Rhus (usually limited to the non-poisonous members of the genus)