noun a rolling, marshy, mossy plain of northern siberia.
2. tundra ·add. ·noun 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.