WordWeb Online

1. Having low density
   "lightheaded from the rarefied mountain air";
   - rare, rarified
    
2. Of high moral or intellectual value; elevated in nature or style
   - exalted, elevated, sublime, grand, high-flown, high-minded, lofty, rarified, idealistic, noble-minded

1. Lessen the density or solidity of
   "The bones are rarefied"
    
2. Make more subtle or refined
   - sublimate, subtilize, subtilise [Brit]
    
3. (chemistry) weaken the consistency of (a chemical substance)
   - attenuate

See also: noble, thin

Type of: alter, change, modify, weaken

Encyclopedia: Rarefied