Related Clues:

• Signal silently
• Acknowledge quietly
• Silently acknowledge
• Acknowledge wordlessly
• Signal silently to
• Acknowledge nonverbally
• Greet wordlessly
• Say yes to without saying 'yes'
• Greet subtly
• Acknowledge surreptitiously, maybe
• Wordlessly greet
• Greet with a head motion
• Slyly signal to
• Signal to