build-up noun

1 gradual increase

ADJ. gradual, slow | steady | rapid | massive VERB + BUILD-UP cause, lead to The leak led to a slow build-up of carbon dioxide. | avoid, prevent

PREP. during/in the ~ | ~ of

2 period of time before an event

ADJ. pre-match, pre-trial, etc.

PREP. ~ to Tension is mounting in the build-up to the elections.