The Collaborative International Dictionary of English v.0.48:

Oscillate \Os"cil*late\ ([o^]s"s[i^]l*l[=a]t), v. i. [imp. & p.
   p. Oscillated ([o^]s"s[i^]l*l[=a]`t[e^]d); p. pr. & vb. n.
   Oscillating ([o^]s"s[i^]l*l[=a]`t[i^]ng).] [L. oscillare to
   swing, fr. oscillum a swing, a little mask or puppet made to
   be hung from trees and swing in the wind, prob. orig., a
   little mouth, a dim. from os mouth. See Oral, and cf.
   Osculate.]
   [1913 Webster]
   1. To move backward and forward; to vibrate like a pendulum;
      to swing; to sway.
      [1913 Webster]

   2. To vary or fluctuate between fixed limits; to act or move
      in a fickle or fluctuating manner; to change repeatedly,
      back and forth.
      [1913 Webster]

            The amount of superior families oscillates rather
            than changes, that is, it fluctuates within fixed
            limits.                               --De Quincey.
      [1913 Webster]

WordNet (r) 3.0 (2006):

oscillate
    v 1: be undecided about something; waver between conflicting
         positions or courses of action; "He oscillates between
         accepting the new position and retirement" [syn: hover,
         vibrate, vacillate, oscillate]
    2: move or swing from side to side regularly; "the needle on the
       meter was oscillating" [syn: oscillate, vibrate]

Moby Thesaurus II by Grady Ward, 1.0:

73 Moby Thesaurus words for "oscillate":
   alternate, back and fill, be here again, bob, bobble, careen,
   change, circle, coggle, come again, come and go, come around,
   come round, come round again, come up again, cycle, dangle, dither,
   ebb and flow, equivocate, flounder, fluctuate, flutter,
   go through phases, hem and haw, intermit, librate, lurch, nutate,
   pendulate, pitch, pulsate, pulse, reappear, recur, reel, reoccur,
   repeat, resonate, return, revolve, ring the changes, rock, roll,
   roll around, rotate, seesaw, shake, shift, shilly-shally, shuffle,
   stagger, swag, sway, swing, teeter, teeter-totter, tergiversate,
   toss, totter, turn, undulate, vacillate, vary, vibrate, wag,
   waggle, wave, waver, wax and wane, wheel, wheel around, wobble