走狗 literally means 'running dog' (a hunting dog that runs ahead), but in modern Chinese it is almost always used as a political insult meaning 'lackey' or 'stooge' — someone who blindly serves a more powerful, often evil, master. This derogatory sense was popularized in Mao-era propaganda to denounce class enemies and imperialist collaborators. The literal 'hunting dog' meaning is rare in everyday speech; you will almost always encounter 走狗 in political or critical contexts.