Source : Webster's Revised Unabridged Dictionary (1913)

Tundra \Tun"dra\, n. [Russ.]
   One of the level or undulating treeless plains characteristic
   of northern arctic regions in both hemispheres. The tundras
   mark the limit of arborescent vegetation; they consist of
   black mucky soil with a permanently frozen subsoil, but
   support a dense growth of mosses and lichens, and dwarf herbs
   and shrubs, often showy-flowered.

Tundra \Tun"dra\, n. [Russ., from a native name.]
   A rolling, marshy, mossy plain of Northern Siberia.

Source : WordNet®

tundra
     n : a vast treeless plain in the arctic regions between the ice
         cap and the tree line