Related Clues:

• Be busily active
• Helicopter sound
• Good engine sound
• Petted pet's sound
• Drum head?
• Background noise
• Forget the lyrics, maybe
• Sound of a well-tuned engine
• Say coquettishly
• Unwanted engine sound
• Pilotless plane
• Go smoothly
• Be catty
• High-pitched metallic sound
• Bothersome engine noise