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

See also: unconquerable, unstoppable

• encephalogram
• encephalography
• encephalomeningitis
• encephalomyelitis
• encephalon
• encephalopathy
• enchain
• enchained
• enchant
• enchanted
• enchanter
• enchanter's nightshade
• enchanting
• enchantingly
• enchantment
• enchantress
• encharge
• enchase
• enchilada
• enchiridion
• enchondroma
• encipher
• encircle
• encircled
• encirclement