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

See also: unconquerable, unstoppable

• Tetragrammaton
• tetrahalide
• tetrahedral
• tetrahedrite
• tetrahedron
• tetrahydrocannabinol
• tetrahymena
• tetraiodothyronine
• tetralogy
• tetralogy of Fallot
• tetramerous
• tetrameter
• tetramethyldiarsine
• tetrametric
• Tetraneuris
• Tetraneuris acaulis
• Tetraneuris grandiflora
• tetranychid
• Tetranychidae
• Tetrao
• Tetrao urogallus
• Tetraodontidae
• Tetraonidae
• tetrapod
• Tetrapturus