Tibetan mastiff

noun
  1. a heavy well-built dog of a Tibetan breed with a long thick coat and a bushy tail carried curled over its back, often used as a guard dog
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012