31er

You say 31er when someone is a betrayer or u cant trust him.
You also say it when u are dissapointed in someone.

31er ist mostley used in the German Language

Examples:

My Friend didn't follow me to the cinema yesterday. He's an 31er!
German: Mein Freund ist gestern nicht mit mir ins Kino gegangen, was ein 31er.
or

My Girlfriend cheated on me what an 31er move.
German: Meine Freundin hat mich betrogen, was ein 31er move.