Source : Webster's Revised Unabridged Dictionary (1913)

Sumac \Su"mac\, Sumach \Su"mach\, n. [F. sumac, formerly sumach
   (cf. Sp. zumaque), fr. Ar. summ[=a]q.] [Written also
   {shumac}.]
   1. (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.

   2. The powdered leaves, peduncles, and young branches of
      certain species of the sumac plant, used in tanning and
      dyeing.

   {Poison sumac}. (Bot.) See under {Poison}.

Source : WordNet®

sumac
     n 1: wood of a sumac
     2: a shrub or tree of the genus Rhus (usually limited to the
        non-poisonous members of the genus) [syn: {sumach}, {shumac}]