unassailable

形容词 unassailable:

1. able to withstand attack
   同义词：impregnable, inviolable, secure, strong, unattackable
2. impossible to assail
   同义词：untouchable
3. without flaws or loopholes
   同义词：unshakable, watertight, bulletproof

1. Her position/argument is unassailable.
   她的立场[论点]是无懈可击的。