That’s a lot of syllables. This is a phrase coined by developmental psychologist Herb Kowplitz. I find it more descriptive than other terms that point to the same thing like emptiness, formlessness, or non-duality.
What these words are pointing to is the observation that despite how things appear to us, there are no discrete boundaries in nature. There is an undifferentiated, continuous flow of energy and information that our perceptual system somewhat arbitrarily parses into bounded objects. Perhaps you've glimpsed this in some moment of transcendence. When you've felt somehow connected to the flow of things around you.
One practical consequence of being able to recognize the undifferentiated phenomenological continuum is that the pervasive sense of separateness and working against the world that many of us carry begins to dissolve.
We can begin to develop a genuine stance of “being in this together” with everything that arises in our experience. This sense of inclusiveness promotes a relaxed and grounded nervous system and a heightened ability to respond to life with creativity and confidence.
This awareness is a gift of the higher reaches of adult development.