relapse[verb]Synonyms:- lapse, backslide, degenerate, fail, regress, revert, slip back
- worsen, deteriorate, fade, fail, sicken, sink, weaken
[noun]Synonyms:- lapse, backsliding, regression, retrogression
- worsening, deterioration, turn for the worse, weakening 
 [TahlilGaran] English Synonym Dictionary ▲
 I.  re‧lapse1 /rɪˈlæps/ 
 verb [intransitive]1.  to become ill again after you have seemed to improve
relapse into We were afraid he might relapse into a coma.2.
 We were afraid he might relapse into a coma.2.  to start to behave badly again
relapse into Clara soon relapsed into her old ways.
 Clara soon relapsed into her old ways. [TahlilGaran] Dictionary of Contemporary English ▲
 II.  re‧lapse2 /rɪˈlæps $ ˈriːlæps/ 
 noun [uncountable and countable][
Date: 1400-1500; 
Language: Latin; 
Origin: past participle of relabi 'to slide back']
 when someone becomes ill again after having seemed to improve: 
 She had a relapse and died soon after.
 She had a relapse and died soon after.  [TahlilGaran] Dictionary of Contemporary English ▲