Solid and sturdy; well-built and durable; not easily broken or damaged.
この金庫は堅牢な作りで、長年使っても安心だ。
This safe is solidly built and reliable even after many years of use.
堅牢な橋を架けるには、専門家による設計が欠かせない。
To build a sturdy bridge, expert design is indispensable.
あの城は石造りで堅牢なため、今でも保存状態がいい。
That castle is built of stone and so sturdy that it remains well preserved even now.