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]