Definition of "high-flown"

Red River Settlement is, to use a high-flown expression, an oasis in the desert, and may be likened to a spot upon the moon or a solitary ship upon the ocean. In plain English, it is an isolated settlement on the borders of one of the vast prairies of North America.

1850, R.M. Ballantyne, Hudson Bay

It seems to me he makes troubles, by expecting every one else to be as quixotic as himself. He is not likely to find high-flown notions among ordinary business men!

1905, Mrs George de Horne Vaizey, A Houseful of Girls