堅固

この城は山の上に築かれた堅固な要塞だった。

The castle was an impregnable fortress built on top of a mountain.

地震に備えて堅固な建物を建てる必要がある。

We need to put up sturdy buildings in preparation for earthquakes.

敵の守りは予想以上に堅固だった。

The enemy's defenses were stronger than expected.

彼は意志が堅固で、一度決めたことは必ずやり遂げる。

He has a firm will and always sees through what he has decided to do.

周囲に反対されても、彼女の決意は堅固だった。

Even when those around her opposed it, her resolve remained firm.

祖母は堅固な信仰を生涯持ち続けた。

My grandmother kept a steadfast faith her whole life.