Source : Webster's Revised Unabridged Dictionary (1913)

Exercise \Ex"er*cise\, v. t. [imp. & p. p. {Exercised}; p. pr. &
   vb. n. {Exercising}.]
   1. To set in action; to cause to act, move, or make exertion;
      to give employment to; to put in action habitually or
      constantly; to school or train; to exert repeatedly; to
      busy.

            Herein do I Exercise myself, to have always a
            conscience void of offence.           --Acts xxiv.
                                                  16.

   2. To exert for the sake of training or improvement; to
      practice in order to develop; hence, also, to improve by
      practice; to discipline, and to use or to for the purpose
      of training; as, to exercise arms; to exercise one's self
      in music; to exercise troops.

            About him exercised heroic games The unarmed youth.
                                                  --Milton.

   3. To occupy the attention and effort of; to task; to tax,
      especially in a painful or vexatious manner; harass; to
      vex; to worry or make anxious; to affect; to discipline;
      as, exercised with pain.

            Where pain of unextinguishable fire Must exercise us
            without hope of end.                  --Milton.

   4. To put in practice; to carry out in action; to perform the
      duties of; to use; to employ; to practice; as, to exercise
      authority; to exercise an office.

            I am the Lord which exercise loving-kindness,
            judgment, and righteousness in the earth. --Jer. ix.
                                                  24.

            The people of the land have used oppression and
            exercised robbery.                    --Ezek. xxii.
                                                  29.

Source : WordNet®

exercising
     n : the activity of exerting your muscles in various ways to
         keep fit; "the doctor recommended regular exercise"; "he
         did some exercising"; "the physical exertion required by
         his work kept him fit" [syn: {exercise}, {physical
         exercise}, {physical exertion}, {workout}]