Definition of rarefy

< rarefied

rarely >

rar·e·fy also rar·i·fy    (râr-f) KEY 

VERB:
rar·e·fied, rar·e·fy·ing, rar·e·fies
VERB:
tr.

1. To make thin, less compact, or less dense.
2. To purify or refine.

VERB:
intr.

To become thin or less compact or dense.

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ETYMOLOGY:
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

OTHER FORMS:
rare·fia·ble(Adjective)