Transliminality is a perceptual - personality construct studied by parapsychologist Michael Thalbourne. This word was invented by Thalbourne, and describes a measure of sensitivity to psychological material (imagery, ideation, affect, and perception) originating in (a) the unconscious, and/or (b) the external environment.
Transliminality has been found to be "a fundamental mechanism in psychology and parapsychology" that overlaps with, but can not be entirely replaced by, personality-related concepts such as "boundary thinness".
Why is this important?
Because it points to a common set of pathways within people that facilitate communication between conscious and unconscious dimensions of experience. This provides a conceptual basis for beginning to look at and talk about things that are happening in our human ecology which may otherwise go unnoticed. It also makes it easier to reconcile extraordinary experiences with the reductive materialist worldview that is presently fashionable, and so provides a useful basis for translating intuition, paranormal phenomena, etc into stories that are not incompatible with this worldview.