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

See also: loud, thunder, unpropitious

• Cassia roxburghii
• Cassia tora
• cassia-bark tree
• cassie
• cassimere
• Cassin's kingbird
• cassino
• Cassiope
• Cassiope mertensiana
• Cassiopeia
• Cassirer
• cassiri
• cassis
• Cassite
• cassiterite
• Cassius
• Cassius Clay
• Cassius Longinus
• Cassius Marcellus Clay
• cassock
• cassocked
• cassoulet
• cassowary
• cast
• cast about