Related Clues:

• Secret signal
• Sign of assent
• ''Hey, over here!''
• A silent bid
• 'Hey you!'
• Whispered sound
• Head motion
• Street peddler's opener?
• Attention getter
• Signal
• Flirt's signal
• Attention-getting sound
• Up-and-down motion
• ''Hey, bud!''
• Cousin of 'ahem'