impregnable vs unassailable

impregnable and unassailable both are adjectives.

Word	Noun	Adjective	Verb	Adverb
impregnable	No	Yes	No	No
unassailable	No	Yes	No	No

As adjectives, impregnable and unassailable are synonyms defined as:

impregnable and unassailable: immune to attack; incapable of being tampered with

Other synonyms of impregnable include inviolable, secure, strong, unattackable.

impregnable (adjective)	unassailable (adjective)
capable of conceiving	without flaws or loopholes
immune to attack; incapable of being tampered with	impossible to assail
incapable of being overcome, challenged or refuted	immune to attack; incapable of being tampered with