reindeer

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

• noun A large deer (Rangifer tarandus) of the Arctic tundra and northern boreal forests, having large hooves and long branched antlers in both sexes, and widely domesticated in Eurasia. Subspecies native to North America and Greenland are usually called caribou.

from The Century Dictionary.

• noun A deer of the genus Rangifer or Tarandus, having horns in both sexes, and inhabiting arctic and cold temperate regions; the Cervus tarandus, Rangifer tarandus, or Tarandus rangifer.
• noun In heraldry, a stag having two sets of antlers, the one pair bending downward, and the other standing erect.

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

• noun (Zool.) Any ruminant of the genus Rangifer, of the Deer family, found in the colder parts of both the Eastern and Western hemispheres, and having long irregularly branched antlers, with the brow tines palmate.
• noun (Bot.) a gray branching lichen (Cladonia rangiferina) which forms extensive patches on the ground in arctic and even in north temperature regions. It is the principal food of the Lapland reindeer in winter.
• noun (Geol.) a name sometimes given to a part of the Paleolithic era when the reindeer was common over Central Europe.

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

• noun zoology An Arctic and Subarctic-dwelling deer with a number of subspecies. The North American subspecies are known as caribou.

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

• noun Arctic deer with large antlers in both sexes; called `reindeer' in Eurasia and `caribou' in North America