Source : Webster's Revised Unabridged Dictionary (1913)

Expedient \Ex*pe"di*ent\, n.
   1. That which serves to promote or advance; suitable means to
      accomplish an end.

            What sure expedient than shall Juno find, To calm
            her fears and ease her boding mind?   --Philips.

   2. Means devised in an exigency; shift.

   Syn: Shift; contrivance; resource; substitute.

Expedient \Ex*pe"di*ent\a. [L. expediens, -entis, p. pr. of
   expedire to be expedient, release, extricate: cf. F.
   exp['e]dient. See {Expedite}.]
   1. Hastening or forward; hence, tending to further or promote
      a proposed object; fit or proper under the circumstances;
      conducive to self-interest; desirable; advisable;
      advantageous; -- sometimes contradistinguished from right.

            It is expedient for you that I go away. --John xvi.
                                                  7.

            Nothing but the right can ever be expedient, since
            that can never be true expediency which would
            sacrifice a greater good to a less.   --Whately.

   2. Quick; expeditious. [Obs.]

            His marches are expedient to this town. --Shak.

Source : WordNet®

expedient
     adj 1: serving to promote your interest; "was merciful only when
            mercy was expedient" [ant: {inexpedient}]
     2: appropriate to a purpose; practical; "in the circumstances
        it was expedient to express loyalty"

expedient
     n : a means to an end; not necessarily a principled or ethical
         one