From the Leri FAQ:

"Metaprogramming is becoming aware that you have been programmed already. That your beliefs and values are simply ideas that have been programmed into your brain and nervous system. It is taking charge of and RE-programming yourself! A most excellent experience."

Dr. John Lilly first coined the term metaprogramming in his seminal work, Programming and Metaprogramming the Human Biocomputer. Lilly was an avid explorer of altered states of consciousness, working with various combinations of isolation, LSD and ketamine explorations, and various mental disciplines. He proposed the notion that inasmuch as the brain can be considered the hardware of the mind, the linguistic models that the brain uses to interpret the world -- programs -- can be modified and refined at the discretion of the metaprogrammer. As the psychedelic explosion began to reverberate across America, Dr. Timothy Leary grabbed hold of the concept, proposing that specific, disciplined approaches to the psychedelic experience can be used to do such metaprogramming.

Since then, metaprogramming has become an umbrella term for any number of approaches to self-improvement/self-refinement. Altered states of consciousness are often, but not always, a factor in metaprogramming; similarly, although the psychedelic experience is often linked to metaprogramming, thanks to Dr. Leary's influence, it is by no means the only nor the "most important" method for metaprogramming. For example, yogic disciplines, various mystic practices and disciplines, shamanic traditions, meditation, and many other consciously directed forms of concentration are used and discussed on Leri with reference to willful and positive metaprogramming.