Webster’s Revised Unabridged Dictionary · 1913
Thundering
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.