If you describe something as ~, you mean that it is vague and not clearly defined or not easy to describe.
The notions we children were able to form of the great world beyond were exceedingly ~...
Music is such a ~ thing.
= vague
ADJ
If you describe something as ~, you mean that it is vague and not clearly defined or not easy to describe.
The notions we children were able to form of the great world beyond were exceedingly ~...
Music is such a ~ thing.
= vague
ADJ
Collins COBUILD. Толковый словарь английского языка для изучающих язык Коллинз COBUILD (международная база данных языков Бирмингемского университета) . 2012