unassailable vs impregnable

unassailable and impregnable both are adjectives.

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

As adjectives, unassailable and impregnable are synonyms defined as:

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

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

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