adjective
[ only before noun ] involving new and interesting ideas which are not yet possible or practical :
The government has been doing some blue-sky thinking on how to improve school standards.
adjective
[ only before noun ] involving new and interesting ideas which are not yet possible or practical :
The government has been doing some blue-sky thinking on how to improve school standards.
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005