Definition of Impregnable

Adjective: impregnable im'preg-nu-bul

Immune to attack; incapable of being tampered with
"an impregnable fortress";
- inviolable, secure, strong, unassailable, unattackable
Capable of conceiving
- conceptive
Incapable of being overcome, challenged or refuted
"an impregnable argument"; "impregnable self-confidence";
- inexpugnable