1. Causing fear or dread or terror
   "horrendous explosions shook the city"
   - awful, dire, direful, dread, dreaded, dreadful, fearful, fearsome, frightening, horrific, terrible

See also: alarming

• iodize
• iodized
• iodoamino acid
• iodochlorhydroxyquin
• iodocompound
• iodoform
• iodoprotein
• iodopsin
• iodothyronine
• iodotyrosine
• IOL
• ion
• ion beam
• ion engine
• ion exchange
• ion pump
• ionate
• Ionesco
• Ionia
• Ionian
• Ionian order
• Ionian Sea
• ionic
• ionic beam
• ionic bond