Synonyms of impregnable

Adjective

1. impregnable, inviolable, secure, strong, unassailable, unattackable, invulnerable (vs. vulnerable)

usage: immune to attack; incapable of being tampered with; "an impregnable fortress"; "fortifications that made the frontier inviolable"; "a secure telephone connection"

2. conceptive, impregnable, fertile (vs. sterile)

usage: capable of conceiving

3. impregnable, inexpugnable, unconquerable (vs. conquerable)

usage: incapable of being overcome, challenged or refuted; "an impregnable argument"; "impregnable self-confidence"

Definition and meaning of impregnable (Dictionary)