From Longman Dictionary of Contemporary Englishhush something ↔ up phrasal verbSECRETto prevent people from knowing about something dishonest or immoral SYN cover up The whole affair was hushed up by the government. → hush→ See Verb table
Examples from the Corpus
hush up• I should only want to hush it up.• I was away at the time, so they decided to hush it up.• In fact I know about one occasion when it was robbed, though they've mostly hushed it up.• The Government hushed it up in the name of trade. 