I bite my thumb at you
You're saying 'I don't respect you.' It's like telling someone they're the worst pizza ever.
I bit my thumb at my friend during the game. He bit me back and we started a fight in the lobby.
She bit her thumb at me in class. I drew a mustache on her face with a marker.
He bit his thumb at the principal. The principal called his mom and made him do push-ups.
xs