rarefied

1 ENTRIES FOUND:
rarefied /ˈrerəˌfaɪd/ adjective
rarefied
/ˈrerəˌfaɪd/
adjective
Britannica Dictionary definition of RAREFIED
[more rarefied; most rarefied]
1 
often disapproving : understood by only a small group of people : only for people who know about a particular thing
2 
technical, of air : not having much oxygen because of being high up in the atmosphere