1. Causing fear or anxiety by threatening great harm
   "a life-threatening disease"
   - dangerous, grave, grievous, serious, severe

See also: critical

• sickleweed golden aster
• sickly
• sickness
• sickness benefit
• sicko
• sickroom
• Sid Caesar
• Sida
• Sida hermaphrodita
• Sida rhombifolia
• Sida spinosa
• Sidalcea
• Sidalcea malviflora
• Siddhartha
• Siddons
• side
• side by side
• side chain
• side chair
• side chapel
• side dish
• side door
• side drum
• side effect
• side entrance