An impregnable fortress is a structure or system that is very difficult to attack or penetrate. This means that the fortress is very difficult to take or break through.

  • The fortress is impregnable because it's built on a steep hill.

  • The fortress is impregnable because it's made out of thick walls and a strong foundation.

Definition of impregnable


immune to attack; incapable of being tampered with


inviolable, secure, strong, unassailable, unattackable


incapable of being overcome, challenged or refuted




capable of conceiving



Nearby Words

impregnable Pronunciation in a video

Example Sentences for impregnable

  • 1

    In that hearing, Butler protested the Fort was impregnable and unassailable.

  • 2

    The cloud is impregnated by rain.

  • 3

    The water is then impregnated the sheet.

  • 4

    Butler claimed the fort was impregnable.

  • 5

    It shouldn't be used to impregnate the egg.

  • 6

    He'll marry and impregnate her.

  • 7

    The country had to be made impregnable.

  • 8

    The fort here is most impregnable.

  • 9

    The rapists can't impregnate their victims.

  • 10

    In the days of horsepower, this was considered an impregnable redoubt.