rarefy
1. [ verb ] make more subtle or refined
Synonyms: subtilize sublimate
Related terms: change
2. [ verb ] lessen the density or solidity (of a substance)
Examples:

"The bones are rarefied"

Related terms: change rarefaction
3. [ verb ] (chemistry) weaken the consistency of (a chemical substance)
Synonyms: attenuate
Related terms: weaken chemistry
Similar spelling:   rarify