1. (verb)rarefy lessen the density or solidity of Synonyms: attenuate, subtilize, sublimate
2. (verb)rarefy, sublimate, subtilize make more subtle or refined Synonyms: purify, rarefy, make pure, distill, subtilize, subtilise, sublimate, attenuate, sublime
3. (verb)rarefy, attenuate weaken the consistency of (a chemical substance) Synonyms: rarefy, attenuate, subtilize, sublimate