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.
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            Ye that . . . perturb so my feast with crying.
                                                  --Chaucer.
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   2. To disorder; to confuse. [R.] --Sir T. Browne.
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