Related Clues:

• [Nudge]
• Fall asleep
• Indicate approval
• Nonverbal approval
• Wynken, Blynken and --
• Audible nudge
• Subtler alternative to "Yo!"
• "Do you want to hear a secret?"
• Utterance before passing a note, maybe
• Covert attention-getter
• Low-key "Hey!"
• Sibilant "Ahem!"
• Signal of comprehension
• "Over here!" sound
• Bit of flirting