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

• sidecar
• sidehill
• sidekick
• sidelight
• sideline
• sidelong
• sideman
• sidepiece
• sidereal
• sidereal day
• sidereal hour
• sidereal month
• sidereal time
• sidereal year
• siderite
• Sideritis
• sideroblast
• sideroblastic anaemia
• sideroblastic anemia
• siderochrestic anaemia
• siderochrestic anemia
• siderocyte
• siderolite
• sideropenia
• siderophilin