borderland

noun2

1. •
   Land near a border; marches.

   • retaining Liddesdale and his other Borderlands and Offices in his owne person — 1644
2. •
   (figurative) An intermediate state, category, etc.

   • “Mr. Alwyn, the line between virtue and foolishness is dim and wavering, and I should hate to see you lost in that marshy borderland. […]” — 1911