The Collaborative International Dictionary of English v.0.48:

Strident \Stri"dent\, a. [L. stridens, -entis, p. pr. of
   stridere to make a grating or creaking noise.]
   Characterized by harshness; grating; shrill. "A strident
   voice." --Thackeray.
   [1913 Webster]

WordNet (r) 3.0 (2006):

strident
    adj 1: conspicuously and offensively loud; given to vehement
           outcry; "blatant radios"; "a clamorous uproar"; "strident
           demands"; "a vociferous mob" [syn: blatant, clamant,
           clamorous, strident, vociferous]
    2: 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]
    3: being sharply insistent on being heard; "strident demands";
       "shrill criticism" [syn: strident, shrill]
    4: unpleasantly loud and harsh [syn: raucous, strident]

Moby Thesaurus II by Grady Ward, 1.0:

94 Moby Thesaurus words for "strident":
   absonant, acid, acidulous, acrid, acrimonious, astringent, atonal,
   biting, bitter, blatant, boisterous, cacophonous, caustic,
   clamorous, cracked, creaking, croaking, cutting, diaphonic,
   disconsonant, discordant, disharmonic, disharmonious, dissonant,
   double-edged, edged, escharotic, fierce, flat, grating, gravelly,
   grinding, guttural, harsh, hoarse, husky, immelodious, incisive,
   inharmonic, inharmonious, jarring, keen, loud, loudmouthed,
   mordacious, mordant, multivocal, musicless, nonmelodious, off,
   off-key, off-tone, openmouthed, out of pitch, out of tone,
   out of tune, penetrating, piercing, poignant, rasping, raucous,
   rigorous, rough, scathing, scraping, scratching, scratchy, severe,
   sharp, shrill, sour, squawky, stabbing, stentorian, stertorous,
   stinging, strident-voiced, stridulant, stridulous, stringent, tart,
   trenchant, tuneless, unharmonious, unmelodious, unmusical,
   untunable, untuned, untuneful, vehement, violent, virulent,
   vitriolic, vociferant