rārē-făcĭo

fēci, factum, 3, v. a.

rarus

I. to make thin or rare, to rarefy (Lucret.): rarefieri, Lucr. 1, 648: rarefacta, id. 2, 1139; 3, 442: rareque facit, id. 6, 233; 870.
Lewis & Short
A Latin Dictionary, 1879
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