1) Aloud 2) Aroar 3) Deafening 4) Earsplitting 5) Loud 6) Noisy 7) Thundery 8) Unpropitious 1) Booming 2) Clapped out 3) Crashing 4) Deafening 5) Earsplitting 6) Extremely ominous 7) Loud 8) Roaring 9) Rolling 10) Thundery 
• (a.) Producing thunder. • (a.) Making a noise like thunder; sounding loud and deep; sonorous.
Thun'der·ous adjective [ Written also thundrous .] 1. Producing thunder. [ R.] « How he before the thunderous throne doth lie.» Milton. 2. Making a noise like thunder; sounding loud and deep; sonorous. -- Thun'der*ous*ly , 
[adj] - extremely ominous
thunder, thunderous, thundery, thunderous, thunderously, thunderousness 1. A booming or crashing noise caused by air expanding along the path of a bolt of lightning. 2. Noise resembling thunder; such as, a loud deep rumbling noise resembling thunder. 3. A manifestation of someone's anger in an explosion of strong words. 4. Etymology: from Middle...
adjective extremely ominous; `world events of thunderous import`