A bird dog can be noun which means a radar detecter.
Or can be a verb which means a law enforcement officer is paying particular attention to a trucker
verb: "That cop has been bird dogging me for the last five miles."
He said: "I'm so frustrated. I called two days ago, and still...no response from customer service."
She replied: "Oh yeah, you have to bird-dog those guys daily to get anything done. They're totally swamped."
B.) (v.) To stare while shading your eyes from the sun with your hand.
C.) (n.) A dog that hunts birds.