A futuristic hypothetical form of addiction, in the form of some kind of neural technology. That is, it does what opiates do, but more faster and more thoroughly. And, even more permanently, it's an even harder addiction to break so very few people do.
I believe the term was popularized by Larry Niven in his 70s-era science fiction. That's certainly where I first encountered it. Under different terminology, it's a central element of Infinite Jest.