an idea or concept that shakes one's previously held beliefs or assumptions about the nature of reality.

To experience a situation which calls into question the way your mind currently sees a certain idea or the world in general. Such an experience usually leaves the person stunned/speechless while he/she begins wrapping his/her mind around the new idea.

Something that seriously fucks with your brain, such as watching Fight Club every night for a week. Trust me on this.

Mindfuck- The process of raping someone's intelligence and/or beliefs with lies and manipulation. The only defense is instinct and intuition; otherwise known as the TRUTH.

to forcibly expose a person to an idea or lesson that leaves he or she, dazed and awestruck, to go through a bout of depression that lasts a variable amount of time in which they question existence, religion, and what they themselves would do in hypothetical situations. Usually the said person will ponder these questions at all hours of the night because they can not sleep and will end up finding only a few answers/revelations. Once of which may include that "if" is the most evil word in the English language. Eventually he or she recovers & usually feels a mixture of a hate & love toward the mind-fucker. Hate for their mental/emotional anguish and love for the perspective they gained and the lesson they learned.

An image that totally fucks with your mind. When you see it, you will shit bricks.