phase speed

phase velocity

noun
  1. physics the speed at which the phase of a wave is propagated, the product of the frequency times the wavelength. This is the quantity that is determined by methods using interference. In a dispersive medium it differs from the group speedAlso called: wave speed, wave velocity
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012