The Collaborative International Dictionary of English v.0.48:

Perturb \Per*turb"\, v. t. [L. perturbare, perturbatum; per +
   turbare to disturb, fr. turba a disorder: cf. OF. perturber.
   See Per-, and Turbid.]
   1. To disturb; to agitate; to vex; to trouble; to disquiet.
      [1913 Webster]

            Ye that . . . perturb so my feast with crying.
                                                  --Chaucer.
      [1913 Webster]

   2. To disorder; to confuse. [R.] --Sir T. Browne.
      [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

110 Moby Thesaurus words for "perturb":
   abash, addle, addle the wits, afflict, agitate, ail, alarm,
   ball up, be the matter, beat, beat up, becloud, bedazzle, befuddle,
   beset, bewilder, bother, bug, burden, churn, churn up, cloud,
   complicate matters, concern, confuse, convulse, daze, dazzle,
   disarrange, discombobulate, discomfit, discomfort, discommode,
   discompose, disconcert, dishevel, dismay, disorder, disorganize,
   disorient, disquiet, distract, distress, disturb, electrify,
   embarrass, embroil, entangle, excite, ferment, flummox, flurry,
   fluster, flutter, fog, fret, fuddle, fuss, harass, inconvenience,
   irk, jar, jolt, jumble, knock galley-west, load with care, maze,
   mist, mix up, moider, muddle, paddle, perplex, perturbate, plague,
   pother, psych, put out, put to it, puzzle, raise hell, rattle,
   rile, ripple, rock, roil, roughen, ruffle, rumple, shake, shake up,
   shock, spook, stagger, stir, stir up, swirl, throw,
   throw into confusion, torment, trouble, unnerve, unsettle, upset,
   vex, whip, whip up, whisk, work up, worry