n.
Pronunciation: ˌ rer- ə - ' fak-sh ə n
Function: noun
Etymology: French or Medieval Latin; French raréfaction, from Medieval Latin rarefaction-, rarefactio, from Latin rarefacere to rarefy
Date: 1572
1 : the action or process of rarefying
2 : the quality or state of being rarefied
3 : a state or region of minimum pressure in a medium traversed by compressional waves (as sound waves)
– rar · e · fac · tion · al \ -shn ə l, -sh ə -n ə l \ adjective