The Collaborative International Dictionary of English v.0.48:

Recidivate \Re*cid"i*vate\ (r[-e]*s[i^]d"[i^]*v[=a]t), v. i.
   [LL. recidivare. See Recidivous.]
   To backslide; to fall again. [Obs.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

recidivate
    v 1: go back to bad behavior; "Those who recidivate are often
         minor criminals" [syn: relapse, lapse, recidivate,
         regress, retrogress, fall back]

Moby Thesaurus II by Grady Ward, 1.0:

35 Moby Thesaurus words for "recidivate":
   backslide, cock, fall, fall again into, fall astern, fall back,
   fall behind, fall from grace, get behind, go backwards, go behind,
   have a relapse, jerk back, lapse, lapse back, lose ground,
   pull back, recede, recur to, regress, relapse, retrocede,
   retroflex, retrograde, retrogress, retrovert, return, return to,
   reverse, revert, revert to, sink back, slide back, slip back,
   yield again to