One of many terms for out-of-the-body travel, also known as OOB, astral projection, or etheric projection. The term ecsomatic is used by parapsychologist Celia E. Green, director of the Institute of Psychophysical Research, Oxford, England, in conjunction with related technical terms, including parasomatic (in which the percipient appears to have another body as distinct from the normal physical body) and asomatic (in which the subject is unaware of having a body).
Green, Celia E. Out-of-the-body Experiences. Proceedings of the Institute of Psychophysical Research, vol. 2. London, 1968.