relapse

verb

1. (intransitive)To fall back again; to slide or turn back into a former state or practice.

   “He has improved recently but keeps relapsing into states of utter confusion.”

   “to relapse into a stupor, into vice, or into barbarism”

   “to relapse into slumber after being disturbed”

   “Then we relapsed into a discomfited silence, and wished we were anywhere else. But Miss Thorn relieved the situation by laughing aloud, and with such a hearty enjoyment that instead of getting angry and more mortified we began to laugh ourselves, and instantly felt better.”

2. (intransitive)To recur; to worsen, be aggravated (after a period of improvement).
3. (informal, intransitive, specifically)To return to a vice, especially self-harm or alcoholism, failing to maintain abstinence.

   “relapsed after 5 months of being clean”

4. To slip or slide back physically; to turn back.

   “You slip your hold and change your side, Relapsing from a necessary guide.”

noun

1. The act or situation of relapsing.

   “a drug relapse”

   “Alas! from what high hope to what relapse / Unlooked for are we fallen!”

2. An occasion when a person becomes ill again after a period of improvement
3. (obsolete)One who has relapsed, or fallen back into error; a backslider.