guard dog

:  one assigned to protect or oversee another: such as

:  a person or a body of persons on sentinel duty

:  troops attached to the person of the sovereign

:  to protect an edge of with an ornamental border

:  to protect from danger especially by watchful attention :  make secure

:  to stand at the entrance of as if on guard or as a barrier

:  canid

:  a highly variable domestic mammal (Canis familiaris) closely related to the gray wolf

:  a male dog

:  canine

:  having an inferior or inauthentic quality :  spurious

:  unlike that used by native speakers or writers

:  to hunt, track, or follow like a hound

:  to worry as if by pursuit with dogs :  plague

:  to bother or pester persistently

:  extremely, utterly