adj. 25B6; adjective
an unassailable fortress : IMPREGNABLE, invulnerable, impenetrable, inviolable, invincible, unconquerable; secure, safe, strong, indestructible.
his logic was unassailable : INDISPUTABLE, undeniable, unquestionable, incontestable, incontrovertible, irrefutable, indubitable, watertight, sound, good, sure, manifest, patent, obvious.
defenceless.