Source : Webster's Revised Unabridged Dictionary (1913)

Fluctuate \Fluc"tu*ate\, v. i. [imp. & p. p. {Fluctuated}; p.
   pr. & vb. n. {Fluctuating}.] [L. fluctuatus, p. p. of
   fluctuare, to wave, fr. fluctus wave, fr. fluere, fluctum, to
   flow. See {Fluent}, and cf. {Flotilla}.]
   1. To move as a wave; to roll hither and thither; to wave; to
      float backward and forward, as on waves; as, a fluctuating
      field of air. --Blackmore.

   2. To move now in one direction and now in another; to be
      wavering or unsteady; to be irresolute or undetermined; to
      vacillate.

   Syn: To waver; vacillate; hesitate; scruple.

   Usage: To {Fluctuate}, {Vacillate}, {Waver}. -- Fluctuate is
          applied both to things and persons and denotes that
          they move as they are acted upon. The stocks
          fluctuate; a man fluctuates between conflicting
          influences. Vacillate and waver are applied to persons
          to represent them as acting themselves. A man
          vacillates when he goes backward and forward in his
          opinions and purposes, without any fixity of mind or
          principles. A man wavers when he shrinks back or
          hesitates at the approach of difficulty or danger. One
          who is fluctuating in his feelings is usually
          vacillating in resolve, and wavering in execution.

Source : WordNet®

fluctuating
     adj : having unpredictable ups and downs; "fluctuating prices"