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

• tension
• tension headache
• tensional
• tensionless
• tensity
• tensive
• tensor
• tensor tympani
• tent
• tent caterpillar
• tent flap
• tent peg
• tent stitch
• tent-caterpillar moth
• tent-fly
• tentacle
• tentacled
• tentacular
• Tentaculata
• tentage
• tentation
• tentative
• tentatively
• tentativeness
• tenter