"Liminal" means "boundary" as in "the veil is thin here"
Liminal spaces are places that feel dreamlike, fuzzy on reality. Their boundaries are unstable. A bus station at night. A long desert highway. A bridge over a river.
They do, however, have an opposite; the Proximal space. These are places that feel far too real, extremely defined, boundaries that seem to override natural forces like time or space. Large warehouses without windows, identical chain stores at disorienting hours, your home after a nap of indeterminate time.