shush
Concise Oxford English Dictionary © 2008 Oxford University Press:
shush /ʃʊʃ, ʃʌʃ/
▶exclamation be quiet. ▶noun
- 1 an utterance of ‘shush’.
- 2 a soft swishing or rustling sound.
- 1 tell or signal to be silent.
■ become or remain silent.
- 2 move with or make a soft swishing or rustling sound.
'shush' also found in these Oxford entries:

