sibilant
1. sib.i.lant \'sib-*-l*nt\ aj [L sibilant-, sibilans, prp. of sibilare to
hiss, whistle, of] imit. origin : having, containing, or producing the
sound of or a sound resembling tha t of the s or the sh in sash {a ~
affricate} {a ~ snake} - sib.i.lant.ly av
2. sibilant n : a sibilant speech sound (as English /s/, /z -, /sh/, /zh/,
/ch(=tsh)/, or /j(=dzh)/)
Webster's English Dictionary