The mystery was a strange internet experiment propagated by the Smashing Pumpkins with their final album before breaking up, Machina. The greater part of what most fans refer to as the mystery occured in the Meaning of Symbols Forum.

Admins for the site gave clues and fans worked with those clues to discover user names and passcodes to open locked sites. Each site almost invariably led to another. There was supposed to be a cartoon featuring the Ghost Children, the otherworldly fans of Glass and the Machines of God, the fictional alter-ego band of the Smashing Pumpkins. However, only about 20 minutes of the cartoon was ever released, in its unfinished form, before the project was dropped.

The whole mystery seemed to just fizzle out with the band, especially once Billy Corgan became preoccupied with Zwan, another musical project. It is a very difficult and convuluted thing to explain. The mystery was something that needs to be experienced to be understood.
What was the point of the Mystery?
by moonbug November 13, 2006
From Invader Zim, Mysterious Mysteries is the show that Dib watches constantly.
Dib: Mysterious Mysteries is on!
Gaz: Why do you have a head?

or

Dib: i finally got pictures of Zim without his disguise, Im sending them to Mysterious Mysteries and then the whole world will know the truth!
by Invader Alice March 10, 2008
Is someone that no matter what would you do, you won't be able to understand them, or to get straight answers, he is the guy/girl who is friends with everyone, can talk to whom they want, but still shares no secrets, no pain, nothing with someone else than themselfs... he is the guy that walks with his hands in his pockets, looks arround once a while, doesnt talk much, probably smokes, and have more than one talent, but doesnt use it to draw other's attention..
-Did you read that poem? its dark and cheerful.
-Well you can never know what *Name* thinks about he is Mysterious
by SilverHeart April 27, 2009
A mysterial is a mystery brake pad material of unknown quality, origin, performance, degradation or composition offered by a brake pad manufacturer for which no fucks are given as they should be focusing on a reliable supply of their popular core product offering.
Today I received a phone call from a manufacturer offering a new mysterial when I can't even get a supply of the popular materials.
by qfm August 19, 2017
Someone or something that is slightly fascinating due to strangeness, being unusual and/or due to a lack of familiarity.
Outer Space is a very mysterious place.
A brilliant mind, made for bettering the world. She sees into the depths and pulls people to the light. She is unknown while knowing everyone. She hides in the caverns of her own soul only to become more extravagant. She is beautifully and intriguingly loyal. She is a mystery.
by PoeticProphetess May 7, 2018
Guy that usually walks around with his hands in his pockets. He is the owner of multiple v-necks he wears on a daily basis. He is boyishly good looking. There is also a high probability that he smokes cigarettes and plays guitar, but for some reason does not use his musical ability to draw women closer to him. You will more than likely spend your entire life wondering what made that person so interesting, even though you knew nothing about him.

girl in coffee house: Man..I wonder who that guy was who performing tonight..I tried to talk to him before he left but he was gone before I could get to him...what a mysterious character.
by Guy with a v-neck June 19, 2008