1. Loud enough to shake the very earth 
2. Sufficiently significant to affect the whole world
   "earthshaking proposals"
   - world-shaking, world-shattering, earth-shattering

See also: important, loud, significant

• Canberra
• cancan
• cancel
• cancel out
• canceled
• cancellate
• cancellated
• cancellation
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• cancer
• cancer body
• Cancer borealis
• cancer cell
• cancer drug
• Cancer irroratus
• cancer juice
• Cancer magister
• cancer of the blood
• cancer of the liver
• Cancer the Crab
• cancerous
• cancerweed
• Cancridae
• cancroid