Definition of "hush up"

hush up

verb
third-person singular simple present hushes up, present participle hushing up, simple past and past participle hushed up
1. (intransitive, informal) To become quiet; to cease making sounds.
2. (transitive, informal) To silence.
3. (transitive) To keep secret, to prevent from becoming known.
  Quotations
  As he took John Willet's view of the matter in regard to the propriety of not bruiting the tale abroad, unless the spirit should appear to him again, in which case it would be necessary to take immediate counsel with the clergyman, it was solemnly resolved that it should be hushed up and kept quiet.
  1841 February–November, Charles Dickens, “Barnaby Rudge”, in Master Humphrey’s Clock, volume II, London: Chapman & Hall, […], chapter 33, page 128