Produced by forcing air through a constricted passage (as 'f'. 's', 'z', or 'th' (in both 'thin' and 'then')); SYN. sibilant, spirant.
(sound) Made by friction of breath forced through narrow passage, as s, f.

A consonant characterized by frictional passage of the expired breath through a narrowing at some point in the vocal tract. See