Short for intellectual belittling syndrome. The main symptom of this syndrome is using a hostile, unprovoked thought-terminating tactic to avoid a real issue at hand in a discussion. This syndrome (also known as IBS) causes usually hostile people to try to diminish others mentally in a variety of fallacious ways and describes a common self-refuting debating tactic. This usually involves discussing a topic and telling someone else (who is perfectly qualified to discuss the issue) they "won't understand it because it's too complicated." This occurs most frequently with respect to discussions about economics, politics, nutrition, and computer programming. Connected with this syndrome is having a chip on one's shoulder and a lack of understanding of the fact that the burden of proof lies on the speaker to justify extraordinary claims.

This term was supposedly invented by Jerry Seinfeld, explaining how his Jewish relatives would come over to his house when he was a kid and try to one-up him in every way possible. At the core of it, an IBS sufferer has deep-seated insecurity issues provoking and propelling their supposed superiority.