Brag's a good dog if he be well set on; but he dare not bite.

The proverb pictures boasting as a dog that looks impressive when urged toward a confrontation but will not bite. Its apparent fierceness does not amount to courage.

It draws a distinction between sounding ready for action and being willing to act. Encouragement may amplify the display without changing what the boaster will actually do.

Use it to challenge a show of confidence, particularly when someone grows louder with encouragement but seems unlikely to follow through. The judgment is skeptical rather than admiring.