Related Clues:

• Sound of contentment
• ''That's the spot!''
• Show pleasure
• Kittenish comment
• 'That's nice!'
• Sound like a well-tuned engine
• Siamese comment
• ''I'm happy'' in Siamese?
• Reaction to a back rub, maybe
• Run smoothly
• Excited exclamation
• 'How nice!'
• Good engine sound
• Petted pet's sound
• Sound of a well-tuned engine