This is a deep thought kind of word, one that describes things as being neither here nor there, but in the process of going from here to there. It is used mainly in technical or medical writing, but I see no reason why we shouldn't start using it to describe all sorts of in-betweens.
adj. 1. occupying a position at, or on both sides of, a boundary or threshold.
Etymology: from Latin, limen/limin, meaning threshold.
Source: Oxford Dictionary
Erin Bedford, writer.