爪牙 originally referred to the claws and fangs of animals, but in modern Chinese it is most commonly used as a derogatory noun meaning 'henchman' or 'lackey' — a person who serves as a ruthless assistant to someone more powerful, often in criminal or corrupt contexts. When used literally, it describes the sharp claws and teeth of beasts. Be aware that the figurative sense carries a strong negative judgment; calling someone 爪牙 is an insult.