From Longman Dictionary of Contemporary Englishhigh-flownˌhigh-ˈflown adjective IMPRESShigh-flown language sounds impressive but does not have much real meaning
Examples from the Corpus
high-flown• Besides, none of them had any sense of humour and I ruined many a high-flown discussion by making jokes.• Such a description might sound high-flown for a small, transitory occasion.• Clark never developed high-flown ideas about saving the world.• And Jack, her husband, had had some high-flown notion of dedicating the lad to the cause.• I should know by now that heavy drinkers are awfully fond of high-flown rationalisations for any brief spell of abstinence. 