Hackering off
When you use your hips like a malfunctioning robot and rub your junk against something dumb, while you pretend it's your crush and they're not a total disaster.
I hacked off in my room because my crush texted me and I was too shy to reply.
I hacked off in the school hallway and my friend saw me and laughed.
I hacked off in the mall and the security guard gave me a look like I was doing something illegal.