1. Hard to defeat
   "an unbeatable ball team" 
2. Incapable of being overcome or subdued
   - invincible, unvanquishable

See also: unconquerable, unstoppable

• rex begonia
• Rex Harrison
• Reye's syndrome
• Reyes
• Reykjavik
• Reynard
• Reynolds
• Rf
• RFD
• Rg
• Rh
• Rh antibody
• Rh factor
• Rh incompatibility
• rh-negative
• Rh-negative blood
• Rh-negative blood type
• rh-positive
• Rh-positive blood type
• rhabdom
• rhabdomancer
• rhabdomancy
• rhabdomyoma
• rhabdomyosarcoma
• rhabdosarcoma