/ ˈsɪbɪlənt; NAmE / adjective , noun
■ adjective
( formal or literary ) making an 's' or 'sh' sound :
the sibilant sound of whispering
■ noun
( phonetics ) a sibilant sound made in speech, such as /s/ and /z/ in the English words sip and zip
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WORD ORIGIN
mid 17th cent.: from Latin sibilant- hissing, from the verb sibilare .