Other forms: hushed, hushing
A hush is a sudden quiet that falls over a room full of people. The lights go down in the theatre and a hush spreads across the audience; a hush after a door slams somewhere upstairs.
It is not quite silence: a hush is silence arriving, and it carries the sense of people holding their breath. As a verb you hush a baby, or hush a friend who is talking too loudly, and 'Hush' on its own is the gentle version of 'Be quiet'. Hushed is the adjective you will need most — hushed voices, a hushed courtroom. To hush something up is to keep an ugly fact out of the newspapers, and hush money is the payment that buys that silence. The word is soft and a little literary; in ordinary speech you would say 'quiet down'.
Hush comes from Middle English huschen. Its older form was husht, used both as a past participle meaning silent and as an interjection meaning 'Quiet!', and English ears heard that final t as a past-tense ending, so a plain new verb hush was cut back out of it. Its relatives sound like what they mean too: German huschen, to scurry, and Danish hysse, to hush.
Middle English
huschen — to hush
English, today
hush
Built from
From Middle English huschen (“to hush”) (as past participle husht (“silent; hushed”) and interjection husht (“quiet!”)). Cognate with Low German huschen, hüssen (“to hush; lull”), German huschen (“to shoo; scurry”), Danish hysse (“to hush”), and maybe Albanian hesht.
Etymology from Wiktionary, CC BY-SA