The Collaborative International Dictionary
Rarification
Rarification \Rar`i*fi*ca"tion\
(r[a^]r`[i^]*f[i^]*k[=a]"sh[u^]n), n.
See Rarefaction. [R.]
--Am. Chem. Journal.
Wiktionary
rarification
n. (alternative form of rarefaction English)