Ego death is a "complete loss of subjective self-identity." The term is used in various intertwined contexts, with related meanings. In Jungian psychology the synonymous term psychic death is used, which refers to a fundamental transformation of the psyche. In the death and rebirth mythology, ego death is a phase of self-surrender and transition, as described by Joseph Campbell in his research on the mythology of the Hero's Journey. It is a recurrent theme in world mythology and is also used as a metaphor in some strands of contemporary western thinking.
In (descriptions of) psychedelic experiences, the term is used synonymously with ego-loss, to refer to (temporary) loss of one's sense of self due to the use of psychedelics. The term was used as such by Timothy Leary et al. to describe the death of the ego in the first phase of an LSD-trip, in which a "complete transcendence" of the self and the "game" occurs. The concept is also used in contemporary spirituality and in the modern understanding of eastern religions to describe a permanent loss of "attachment to a separate sense of self" and self-centeredness. This conception has influential part in Eckhart Tolle's teaching, where Ego is presented as an accumulation of thoughts and emotions, and only by de-identifying one’s consciousness from it can one truly be free from suffering (in the Buddhist meaning).
Various definitions can be found of ego death.
Daniel Merkur:
... an imageless experience in which there is no sense of personal identity. It is the experience that remains possible in a state of extremely deep trance when the ego-functions of reality-testing, sense-perception, memory, reason, fantasy and self-representation are repressed [...] Muslim Sufis call it fana (annihilation), and medieval Jewish kabbalists termed it "the kiss of death."
Ventegodt and Merrick:
... a fundamental transformation of the psyche. Such a shift in personality has been labeled an "ego death" in Buddhism or a psychic death by Jung.