unbeatable
1. [ adjective ] hard to defeat
Examples:

"an unbeatable ball team"

Related terms: unstoppable
2. [ adjective ] incapable of being overcome or subdued
Synonyms: invincible unvanquishable
Examples:

"an invincible army" "her invincible spirit"

Related terms: unconquerable
Similar spelling:   unobtainable
  unfathomable
  unbeaten
  unabated