rarefy rarefy /ˈrɛrəfaɪ/

verb

1. (chemistry) weaken the consistency of (a chemical substance)  ( attenuate , rarefy )
   (chemistry) weaken the consistency of (a chemical substance)
   
2. Make more subtle or refined  ( rarefy , sublimate , subtilize )
   make more subtle or refined
   
3. Lessen the density or solidity of  ( rarefy )
   lessen the density or solidity of
    The bones are rarefied
   The bones are rarefied