The expression describes a puzzle, sometimes a crossword, characterised by its substantial issue and complexity. It suggests a puzzle that’s difficult to resolve, requiring appreciable effort and data from the solver. For instance, a particular themed crossword with obscure vocabulary and complicated wordplay is perhaps characterised utilizing this phrase.
Such puzzles present a big cognitive exercise, stimulating problem-solving expertise and increasing vocabulary. They will provide a way of accomplishment upon completion because of the issue concerned. Crosswords of this nature have existed for many years, evolving from easier phrase puzzles to extra advanced and difficult constructions, reflecting rising solver ability and expectations.