Meaning of “gradual” - Learner’s Dictionary

gradual

adjective us uk /ˈɡrædʒuəl/
The change has been gradual.There's been a gradual decline in visitors to the museum.There's been a gradual improvement in the school's performance.We have noticed a gradual increase in prices.Getting over someone's death is a very gradual process.

B2 happening slowly over a period of time:

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