One entry found for
rarefaction.
Main Entry:
rar·efac·tion 
Pronunciation:
rar-
-
fak-sh
n,
rer-
Function:
noun
1 : the action or process of rarefying
2 : the state of being rarefied
3 : a state or region of minimum pressure in a substance (as air) being traveled through by a wave formed by compression (as sound)