Liminal
Technically, “limen” is the threshold for perception. So, a liminal thing is something occurring at the minimum threshold for perception. For example, a liminal sound is one that you can just barely hear – it’s right at the edge of what is perceptible and what is not.
(Something that does not cross this threshold is “subliminal.”)
More generally, the word is used to explain concepts and things that are between two states – sort of a “half on” situation. Like a “liminal friendship” or “liminal credibility.”
Why I Looked It Up
I weirdly encountered it a number of times in quick succession, but here’s an example from a review of Emily Ratatowski’s book:
My Body sits in this liminal space between reappraisal and self-defense.
Postscript
Added on
An article about American suburbs provides this explanation:
Images […] dubbed “liminal spaces,” are pretty popular on the internet. These scenes depict a transitory space: A hallway might be one example, but so is an empty room with an open door on the opposite side – or even a parking lot or empty street. You know you are not meant to linger there; your destination lies somewhere ahead. But these images of familiar spaces are also always denuded of people, and often of other life, or ornamentation in general. They invoke a sense of uncanniness, uncertainty, and isolation.
[…] American suburbs are full of ugly, empty, liminal spaces: spaces you are not meant to linger in or enjoy. They’re the creepy hallways of the built environment, and you can’t feel comfortable traversing them unless you’re zooming past them in a car. Why should we fill our cities and towns with places like this? Would you want to live in a house full of empty hallways? I wouldn’t.