Using your index and middle finger
to squeeze someone's nipple; "the power of two becoming one"; can add "power" as a prefix to denote hard or rough; can indicate holidays (e.g., Merry Tweaksmas; Happy Tweaksgiving; St. Patweak's Day)
"It's time for your tweaking--give up those tender nipple buds!"
"We wish you a Merry Tweaksmas and a Happy New Tweak Year!"
"Okay, you can tweak me, but no power tweaks. Got it?"