sibilant
sib-i-lant
adjective
Making or characterised by a strong hissing or whistling sound.
"Her sibilant whisper was hard to hear."
noun
A speech sound produced with a distinct hissing effect.
"The 'sh' sound is a sibilant."
Thesaurus
Synonyms: sibilant consonant, continuant, fricative, strident, spirant, soft