Definitions
1.adjectiveDistant from the lives and everyday concerns of ordinary people; esoteric, exclusive, select."Philosophical debates can be quite rarefied."
2.adjectiveElevated in style or nature, sublime; of high intellectual or moral value.
3.adjective(of a gas etc.) Less dense than usual; thin."The air at high altitudes at the top of mountains is rarefied."
4.verbTo make rare, thin, porous, or less dense
5.verbTo expand or enlarge without adding any new portion of matter to.