A euphemism of 'fuck you'. When spoken aloud, 'cuff' has the same kind of dirty, short impact of 'fuck', and almost everyone still knows what you're getting across.
When a guy stays arm-in-arm with his girl all night long at the club (or any public place), trying to keep other guys from talking to her. For instance, he might walk her to the bathroom, then stay outside the bathroom waiting for her, then walk her back to the dance floor.
In R. Kelly and Bow Wow's song "I'mma Flirt," there's a verse that goes "cuff your chick." Basically he's warning guys to "cuff their chicks" cause he's a flirt! >;-P
Regulating your chick when she's acting all buck wild.
Showing who's boss; showing who wears the pants in the relationship.
::Girlfriend bickering to you about nonsense in front of your friends::
friend #1: cuff your chick, she's getting annoying.
friend #2: yeah man, you are the one wearing the pants in the relationship right?, well then regulate.
The thing lesbians and other female members of the LGBTQIA+ community do to show that they are, in fact, a female member of the LGBTQIA+ community that can develop feeling for another female (who is not always a member of the LGBTQIA+ community and is usually their best friend)
*Could also be used as a metaphorical phrase that helps you let other people know you like girls, even though you might be wearing a skirt at the moment
Girl 1: Do you cuff your jeans?
Girl 2: Yea... Do you?
Girl 1: Yes, I cuff my jeans!
***
Girl A: Hey, I just wanted to let you know I cuff my jeans!
Girl B: But... You're in a skirt...
Girl A: Nevermind, that's not what I meant