In Zen, unpleasant or distracting thoughts or illusions that occur during zazen. The term makyo is a Zen term that means “ghost cave” or “devil’s cave.” It is a figurative reference to the kind of self-delusion that results from clinging to an experience and making a conceptual “nest” out of it for oneself. Makyo is essentially synonymous with illusion, but especially in reference to experiences that can occur within meditation practice.
In Philip Kapleau's The Three Pillars of Zen, Yasutani Roshi explained the term as the combination of ma meaning devil and kyo meaning the objective world. This character for “devil” can also refer to Mara, the Buddhist “tempter” figure; and the character kyo can mean simply region, condition or place. Makyo refers to the hallucinations and perceptual distortions that can arise during the course of meditation and can be mistaken by the practitioner as "seeing the true nature" or kensho. Zen masters warn their meditating students to ignore sensory distortions. These can occur in the form of visions and perceptual distortions, but they can also be experiences of blank, trance-like absorption states. In the Zen school, it is understood that neither category of experience – however fascinating they may be – is a true and final enlightenment.
Contemplative literature contains numerous descriptions of the perceptual distortion produced by meditation. It is characterized in some schools as "going to the movies," a sign of spiritual intensity but a phenomenon that is considered distinctly inferior to the clear insight of settled practice. In some Hindu schools it is regarded as a product of the sukshma sharira, or "experience body," in its unstable state, and in that respect is seen to be another form of maya, which is the illusory nature of the world as apprehended by ordinary consciousness.
Tibetan contemplative literature uses the parallel term nyam, which fall into three categories, usually listed as clarity, bliss, and non-conceptuality. Many types of meditation phenomena can be classed under this rubric, and are generally tied to the reorganization of the body's subtle energies that can occur in meditation. See Dudjom Lingpa, (cited in Wallace, the Attention Revolution), and Padmasambhava (in Treasures from the Juniper Ridge) for more specific examples. Robert Aitken Roshi classifies speaking in tongues as "elaborate makyo" (Taking the Path of Zen).