Meaning of “relapse” - Learner’s Dictionary

relapse

noun [ C, U ] us uk /rɪˈlæps, ˈriːlæps/
SICK

an occasion when someone becomes sick again after a period of feeling better:

I had / a relapse last year and was off work for a month.
WORSE

an occasion when something or someone gets worse again after being better:

The company's share prices have suffered a relapse this week.
relapse verb [ I ] us uk /rɪˈlæps/

(Definition of “relapse” from the Cambridge Learner’s Dictionary © Cambridge University Press)