That’s the Word for It: Luftmensch

You must have met dreamers with their heads in the clouds and who face trouble with the practical nitty-gritty of living. The Yiddish language has a word for such a person- luftmensch, where luft connotes air and mensch means human being.

Found a quote featuring this word:

Luftmensch—the impractical individual whose imagination has lifted him beyond the world.”
― Stephen Eric Bronner, Critical Theory: A Very Short Introduction