rarefy

rar·e·fy also rar·i·fy  (râr-f)

v. rar·e·fied also rar·i·fied, rar·e·fy·ing also rar·i·fy·ing, rar·e·fies also rar·i·fies

v.tr.

1. To make thin, less compact, or less dense.

2. To purify or refine.

v.intr.

To become thin or less compact or dense.

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[Middle English rarefien, from Old French rarefier, from Medieval Latin rrificre, alteration of Latin rrfacere : rrus, rare + facere, to make; see dh- in Indo-European roots.]

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rare·fia·ble adj.

Thesaurus

Verb	1.	rarefy - lessen the density or solidity of; "The bones are rarefied" alter, change, modify - cause to change; make different; cause a transformation; "The advent of the automobile may have altered the growth pattern of the city"; "The discussion has changed my thinking about the issue"
	2.	rarefy - make more subtle or refined sublimate, subtilize alter, change, modify - cause to change; make different; cause a transformation; "The advent of the automobile may have altered the growth pattern of the city"; "The discussion has changed my thinking about the issue"
	3.	rarefy - weaken the consistency of (a chemical substance) attenuate chemical science, chemistry - the science of matter; the branch of the natural sciences dealing with the composition of substances and their properties and reactions weaken - lessen the strength of; "The fever weakened his body"