unassailable

/ˌʌnəˈseɪləbəl/
adjective
  1. Impossible to attack, question, or defeat; completely secure or certain.
    • She presented an unassailable argument that convinced everyone in the room.
    • The fortress was built on a cliff, making it virtually unassailable.
    • The team's lead in the final minutes seemed unassailable.
What does "unassailable" mean? | whatsthatwordmean | whatsthatwordmean