The Collaborative International Dictionary of English v.0.48:

Deviate \De"vi*ate\, v. i. [imp. & p. p. Deviated; p. pr. &
   vb. n. Deviating.] [L. deviare to deviate; de + viare to
   go, travel, via way. See Viaduct.]
   To go out of the way; to turn aside from a course or a
   method; to stray or go astray; to err; to digress; to
   diverge; to vary.
   [1913 Webster]

         Thus Pegasus, a nearer way to take,
         May boldly deviate from the common track. --Pope.

   Syn: To swerve; stray; wander; digress; depart; deflect; err.
        [1913 Webster]