impregnable vs unattackable

impregnable and unattackable both are adjectives.

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

As adjectives, impregnable and unattackable are synonyms defined as:

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

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

impregnable (adjective)	unattackable (adjective)
capable of conceiving	immune to attack; incapable of being tampered with
immune to attack; incapable of being tampered with
incapable of being overcome, challenged or refuted