WordNet Dictionary- [adj] extraordinarily big or impressive; "a thundering success"; "the thundering silence of what was left unsaid"
- [adj] sounding like thunder; "the thundering herd"
Webster's 1913 Dictionary\Thun"der*ing\, a. 1. Emitting thunder. Roll the thundering chariot o'er the ground. --J. Trumbull. 2. Very great; -- often adverbially. [Slang] -- {Thun"der*ing*ly}, adv.\Thun"der*ing\, n. Thunder. --Rev. iv. 5.