1. Loud enough to cause (temporary) hearing loss
   - deafening, earsplitting, thundery 
2. Extremely ominous
   "world events of thunderous import"

See also: loud, thunder, unpropitious

• organic chemistry
• organic compound
• organic disorder
• organic evolution
• organic fertiliser
• organic fertilizer
• organic law
• organic light-emitting diode
• organic phenomenon
• organic process
• organic structure
• organically
• organicism
• organicistic
• organification
• organisable
• organisation
• organisation chart
• Organisation for the Prohibition of Chemical Weapons
• Organisation of Petroleum-Exporting Countries
• Organisation of the Oppressed on Earth
• organisational
• organisational chart
• organise
• organised