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 selected themed crossword with obscure vocabulary and complex wordplay is perhaps characterised utilizing this phrase.
Such puzzles present a major cognitive exercise, stimulating problem-solving abilities and increasing vocabulary. They will provide a way of accomplishment upon completion as a result of issue concerned. Crosswords of this nature have existed for many years, evolving from less complicated phrase puzzles to extra complicated and difficult constructions, reflecting rising solver ability and expectations.