1. immune to attack; incapable of being tampered with (Freq. 1) - an impregnable fortress - fortifications that made the frontier inviolable - a secure telephone connection • Syn: inviolable, secure, strong, unassailable, unattackable • Similar to: invulnerable • Derivationally related forms: impregnability, secureness (for: secure) 2. capable of conceiving • Syn: conceptive • Similar to: fertile • Derivationally related forms: conceive (for: conceptive) 3. incapable of being overcome, challenged or refuted - an impregnable argument - impregnable self-confidence • Syn: inexpugnable • Similar to: unconquerable
