Akademik

sibilant

adj. & n.
—adj.
1 (of a letter or set of letters, as s, sh) sounded with a hiss.
2 hissing (a sibilant whisper).
—n. a sibilant letter or letters.
Derivatives:
sibilance n. sibilancy n.
Etymology: L sibilare sibilant- hiss

Useful english dictionary. 2012.