cumulateverb
/ˈkjuː.mjʊ.leɪt/[ T ] to collect a large amount of something over a period of time by gradually adding more:
The system has the ability to cumulate data over a number of years.
They have cumulated debts of over $10 million.
[ I ] to gradually increase by combining with other things over a period of time:
These small delays can cumulate and become a problem.