1. Immune to attack; incapable of being tampered with
   - impregnable, inviolable, secure, strong, unassailable

See also: invulnerable

• stilbestrol
• stilbite
• stilboestrol
• stile
• stiletto
• stiletto heel
• still
• still life
• Still's disease
• still-fish
• still-hunt
• stillage
• stillbirth
• stillborn
• stillborn infant
• stillness
• stillroom
• Stillson wrench
• stilly
• stilt
• stilt plover
• stiltbird
• stilted
• stiltedly
• Stilton