31er refers to a person who betrays his friends and other close people. The expression originates from Germany, where a person may receive a lighter punishment for drug offenses if they help law enforcement catch other offenders (paragraph 31 of the German Narcotics Act).
We wouldn't have been caught for the prank if it hadn't been for John—he's such a 31er!
by Venomist June 19, 2019
Get the 31er mug.
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.
by asseater31 December 27, 2018
Get the 31er mug.