Related Clues:

• "Grrr!" is one
• Lab alert?
• Frustrated sound
• Angry dog's warning
• Speak harshly
• Boxer's "Back off!"
• [Return that bone at once, or I shall bare my teeth and yip!]
• [Mumble, mumble]
• Guard dog's warning
• "I'm mad!"
• Dog's sound
• Warning from a boxer
• Lock problem
• [This is frustrating!]
• Sound from a junkyard dog