Meaning of rotation of axes

rota'tion of ax'es

Pronunciation: (ak'sēz), [key]
— Math. Math.
  1. a process of replacing the axes in a Cartesian coordinate system with a new set of axes making a specified angle with and having the same origin as the original axes.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.