guard dog

or guard·dog

See more synonyms for guard dog on Thesaurus.com
noun
  1. a large, aggressive dog, as a German shepherd or Doberman pinscher, trained to guard persons or property and often to attack or restrain on command.

Origin of guard dog

First recorded in 1790–1800
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words for guard dog

bandog, watchdog