The Collaborative International Dictionary of English v.0.48:

Thunder \Thun"der\, v. i. [imp. & p. p. Thundered; p. pr. &
   vb. n. Thundering.] [AS. [thorn]unrian. See Thunder, n.]
   1. To produce thunder; to sound, rattle, or roar, as a
      discharge of atmospheric electricity; -- often used
      impersonally; as, it thundered continuously.
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            Canst thou thunder with a voice like him? --Job xl.
                                                  9.
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   2. Fig.: To make a loud noise; esp. a heavy sound, of some
      continuance.
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            His dreadful voice no more
            Would thunder in my ears.             --Milton.
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   3. To utter violent denunciation.
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The Collaborative International Dictionary of English v.0.48:

Thundering \Thun"der*ing\, a.
   1. Emitting thunder.
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            Roll the thundering chariot o'er the ground. --J.
                                                  Trumbull.
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   2. Very great; -- often adverbially. [Slang]
      [1913 Webster] -- Thun"der*ing*ly, adv.
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The Collaborative International Dictionary of English v.0.48:

Thundering \Thun"der*ing\, n.
   Thunder. --Rev. iv. 5.
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WordNet (r) 3.0 (2006):

thundering
    adj 1: sounding like thunder; "the thundering herd"
    2: extraordinarily big or impressive; "a thundering success";
       "the thundering silence of what was left unsaid"