WordNet sense 1 (a continuant consonant produced by breath moving against a narrowing of the vocal tract):

spirant, fricative consonant

WordNet sense 2 (of speech sounds produced by forcing air through a constricted passage (as `f', `s', `z', or `th' in both `thin' and `then')):

sibilant, strident, continuant

WordNet sense 3 ((of speech sounds); produced with the back of the tongue raised toward the hard palate; characterized by a hissing or hushing sound (as `s' and `sh')):

soft