Related Clues:

• Kettle sound
• They're not part of the body: Abbr.
• Snake sound
• Heckle, in a way
• They follow signatures
• Greet the villain
• Sound of disapproval
• Ophidian sound
• Quick addenda
• Ends of letters, briefly
• Vent sound
• Greeting for the villain
• Snake's warning
• Radiator sound
• Serpent's sound