quiescent
Concise Oxford English Dictionary © 2008 Oxford University Press:
quiescent /kwɪˈɛs(ə)nt, kwʌɪ-/
▶adjective in a state or period of inactivity.
– derivatives
quiescence noun,
quiescently adverb.
quiescence noun,
quiescently adverb.
– origin C17: from L. quiescent-, quiescere ‘be still’, from quies ‘quiet’.
'quiescent' also found in these Oxford entries:

