1. A failure to maintain a higher state
   "His relapsing into old habits disappointed his mentor";
   - backsliding, lapse, lapsing, relapse, reversion, reverting

1. Deteriorate in health
   "he relapsed";
   - get worse
    
2. Go back to bad behaviour
   "Those who relapse are often minor criminals";
   - lapse, recidivate [rare], regress, retrogress, fall back

Type of: change state, failure, regress, retrovert [rare], return, revert, turn, turn back

Encyclopedia: Relapsing