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

See also: invulnerable

• sucrase
• sucre
• sucrose
• suction
• suction cup
• suction curettage
• suction lipectomy
• suction pump
• suction stop
• suctorial
• Sudafed
• Sudan
• Sudanese
• Sudanese monetary unit
• Sudanese pound
• sudate
• sudation
• sudatorium
• sudatory
• Sudbury
• sudd
• sudden
• sudden death
• sudden infant death syndrome
• suddenly