mastiff

English Thesaurus

1. an old breed of powerful deep-chested smooth-coated dog used chiefly as a watchdog and guard dog (noun.animal)

hypernym	:	working dog,
definition	:	any of several breeds of usually large powerful dogs bred to work as draft animals and guard and guide dogs (noun.animal)

hyponym	:	tibetan mastiff,
definition	:	very large powerful rough-coated dog native to central Asia (noun.animal)