fortresslike

As a noun terms

is .

As an adjective fortresslike is

resembling a fortress in shape or impregnability.

As a noun impregnability

is the quality or state of being impregnable; invincibility.

As an adjective fortresslike is

resembling a fortress in shape or impregnability.

As a noun fortress

is a fortified place; a large and permanent fortification, sometimes including a town; a fort; a castle; a stronghold; a place of defense or security.

As a verb fortress

is to furnish with a fortress or with fortresses; to guard; to fortify.

As an adjective fortresslike is

resembling a fortress in shape or impregnability.