Source : Webster's Revised Unabridged Dictionary (1913)

Retreat \Re*treat"\, v. i. [imp. & p. p. {Retreated}; p. pr. &
   vb. n. {Retreating}.]
   To make a retreat; to retire from any position or place; to
   withdraw; as, the defeated army retreated from the field.

         The rapid currents drive Towards the retreating sea
         their furious tide.                      --Milton.

Source : WordNet®

retreating
     adj : moving back or away [ant: {advancing}]