sibilant

from WordNet (r) 3.0 (2006)

sibilant
    adj 1: of speech sounds produced by forcing air through a
           constricted passage (as `f', `s', `z', or `th' in both
           `thin' and `then') [syn: {fricative}, {continuant},
           {sibilant}, {spirant}, {strident}]
    n 1: a consonant characterized by a hissing sound (like s or sh)
         [syn: {sibilant}, {sibilant consonant}]

from The Collaborative International Dictionary of English v.0.48

Sibilant \Sib"i*lant\, a. [L. sibilans, -antis, p. pr. of
   sibilare to hiss: cf. F. sibilant.]
   Making a hissing sound; uttered with a hissing sound;
   hissing; as, s, z, sh, and zh, are sibilant elementary
   sounds. -- n. A sibiliant letter.
   [1913 Webster]

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