Source : Webster's Revised Unabridged Dictionary (1913)

Transient \Tran"sient\, a. [L. transiens, -entis, p. pr. of
   transire, transitum, to go or pass over. See {Trance}.]
   1. Passing before the sight or perception, or, as it were,
      moving over or across a space or scene viewed, and then
      disappearing; hence, of short duration; not permanent; not
      lasting or durable; not stationary; passing; fleeting;
      brief; transitory; as, transient pleasure. ``Measured this
      transient world.'' --Milton.

   2. Hasty; momentary; imperfect; brief; as, a transient view
      of a landscape.

   3. Staying for a short time; not regular or permanent; as, a
      transient guest; transient boarders. [Colloq. U. S.]

   Syn: {Transient}, {Transitory}, {Fleeting}.

   Usage: Transient represents a thing as brief at the best;
          transitory, as liable at any moment to pass away.
          Fleeting goes further, and represents it as in the act
          of taking its flight. Life is transient; its joys are
          transitory; its hours are fleeting.

                What is loose love? A transient gust. --Pope

                If [we love] transitory things, which soon
                decay, Age must be loveliest at the latest day.
                                                  --Donne.

                O fleeting joys Of Paradise, dear bought with
                lasting woes.                     --Milton.
          -- {Tran"sient*ly}, adv. -- {Tran"sient*ness}, n.

Source : WordNet®

transiently
     adv : for a very short time; "these three pions may actually be
           joined together transiently as a compound particle
           during the interchange process"