A state of joined shamatha and vipashyana focused conceptually or non-conceptually on space-like voidness (emptiness).
A state of mind having the joined pair of shamatha and vipashyana, and in which absorbed concentration is focused single-pointedly on a voidness that is like space. It may be either conceptual or nonconceptual. Sometimes translated as "meditative equipoise."
J Hopkins: meditative equipoise.