The Collaborative International Dictionary of English v.0.48:

Resonant \Res"o*nant\ (-nant), a. [L. resonans, p. pr. of
   resonare to resound: cf. F. r['e]sonnant. See Resound.]
   1. Returning, or capable of returning, sound; fitted to
      resound; resounding; echoing back.
      [1913 Webster]

            Through every hour of the golden morning, the
            streets were resonant with female parties of young
            and old.                              --De Quincey.
      [1913 Webster]

   2. (Elec.) Adjusted as to dimensions (as an electric circuit)
      so that currents or electric surgings are produced by the
      passage of electric waves of a given frequency.
      [Webster 1913 Suppl.]

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "resonant":
   beating, booming, consonant, deep, earsplitting, electrifying,
   enhanced, fat, fluctuant, fluctuating, fluctuational, full,
   harmonic, heightened, intensified, libratory, loud, mellow, noisy,
   nutational, orotund, oscillating, oscillatory, pendular, pendulous,
   periodic, plangent, powerful, profound, pulsating, pulsing,
   resonating, resounding, reverberant, reverberating, rich, ringing,
   rolling, rotund, round, sonorous, sounding, stentorian, strident,
   thrilling, throbbing, thundering, thunderous, vacillating,
   vacillatory, vibrant, vibratile, vibrating, vibratory, wavering