A Thing
A thing is when you do something embarrassing, weird, or just plain stupid and you don't want to explain it. It's like a secret you keep to yourself.
I did a thing with my math teacher during lunch. I still don't know what it was.
My sister did a thing with the school principal. He didn't fire her, so it was worth it.
My friend did a thing with the bus driver. Now he knows my name.