Related Clues:

• Signal, perhaps
• Greet nonverbally
• Bob one's head at
• Acknowledge silently
• Say 'yes' to silently
• Acknowledge in passing
• Give a nonverbal 'OK'
• Acknowledge with a head movement
• Agree with, tacitly
• Silently agree to
• Signal agreement
• Tacitly agree with
• Silently greet
• Signal silently
• Greet quietly