In psychology, egolessness is an emotional state where one feels no ego (or self); of having no distinct being apart from the world around oneself. From the view of Western psychoanalysis and therapy, the state of "oneness" can be either positive or negative depending on the patient, and in the context in which these feelings occur in each patient.
The described feeling of oneness (of being inextricably woven to the fabric of one's surroundings or environment) is thought to be akin to egolessness. Lifestyles of communal ownership (no individual property) and the "vow of poverty" in many monastic traditions may also be intended to make selflessness easier to maintain; that its practitioners may continuously remain in a meditative state of mind.
In some forms of meditation in Asian religions, egolessness is a mental state that is sought after. While at the basic levels, meditation is geared toward relaxation, the practice of advanced meditators may be aimed toward the purpose of dividing one from their awareness of "self," to a certain degree, and for a certain time. The ritual and religious treatment of meditation functions so that the individual learns to take the practice with seriousness; learning to gradually control their degree of relaxation such that undesired and harmful schisms do not occur to the psyche.
Note that the term "selflessness" is similar in literal meaning (ego is the Greek word for "I") but differs in nuance and usage. One would describe a set of acts as "selfless" (altruistic) when they are not selfish—when they benefit others more than oneself. One would say that a person is "egoless" when he or she feels or acts in a way that suggests that the self is irrelevant (regardless of whether the act or attitude had any benefit to self or others). In other words, "selfless" is the opposite of "selfish" while "egoless" is orthogonal to both. The closest antonyms to "egolessness" are "egotism" (a heightened sense of self worth or one's own importance) or possibly solipsism.
The writer Aleister Crowley distinguished between two main types of egolessness, for which he used the Sanskrit terms Dhyana (which means "meditation") and Samadhi (which he associated with the Nothing, or in Hebrew Ain). He wrote the following about the relative difficulties of attaining them:
Now we do know this, that if thought is kept single and steady, Dhyana results. We do not know whether an intensification of this is sufficient to cause Samadhi, or whether some other circumstances are required. One is science, the other empiricism. 
Despite this, Crowley recommended a complex system of practices from Eastern and Western sources to help people attain Samadhi.
Ego loss is commonly experienced by those under the influence of psychedelic drugs.
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