WordNet (r) 3.0 (2006):

Siberia
    n 1: a vast Asian region of Russia; famous for long cold winters

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "Siberia":
   Alaska, Antarctic Zone, Antarctica, Arctic Circle, Arctic Zone,
   China, Darkest Africa, Frigid Zones, God knows where, Greenland,
   Iceland, Lower Slobbovia, North Pole, Novaya Zemlya,
   Outer Mongolia, Pago Pago, Pillars of Hercules, South Pole, Thule,
   Tierra del Fuego, Timbuktu, Ultima Thule, Yukon, antipodes,
   frontier, godforsaken place, jumping-off place, nowhere, outback,
   outer space, outpost, outskirts, pole, the Antarctic, the Arctic,
   the Great Divide, the Hebrides, the South Seas, the Yukon,
   the boondocks, the moon, the sticks, the tullies, tundra