Of a threshold. Occupying an in-between state where categories loosen and transition is the main fact. Neither one thing nor the other, but poised, unsettled, and charged (literary; also anthropological). Where intermediate can be purely measurable, liminal implies atmosphere, the strange electricity of crossing.

From Latin limen "threshold." First a physical edge, then a concept. The doorway becoming a way to think about rites, passages, and the eerie familiar of "almost."