Definitions for "Rarefaction"
The act or process of rarefying; the state of being rarefied; -- opposed to condensation; as, the rarefaction of air.
An area of high air pressure that acts as the wave trough for sound waves. The spacing between successive rarefactions is the wavelength of sound, and the number of successive areas of rarefaction that arrive at the ear per second is the frequency, or pitch, of the sound.
the region between compressions in a longitudinal wave.