borderland

Land near a border; marches.

retaining Liddesdale and his other Borderlands and Offices in his owne person

1850, Charlotte Brontë, letter dated 16 March, 1850, in The Life of Charlotte Brontë by Elizabeth Gaskell, London: Smith, Elder, 1857, Volume 2, Chapter , p. , some of the ancient East Lancashire families, whose mansions lie on the hilly border-land between the two counties

An intermediate state, category, etc.

Near-synonyms: twilight zone, shadowland

Is he [the Scotchman] orthodox—he has no doubts. Is he an infidel—he has none either. Between the affirmative and the negative there is no border-land with him. You cannot hover with him upon the confines of truth, or wander in the maze of a probable argument.