Ironclad

(a.) Clad in iron; protected or covered with iron, as a vessel for naval warfare.

Ironclad - Other Definitions

(a.) Clad in iron; protected or covered with iron, as a vessel for naval warfare.
(a.) Rigorous; severe; exacting; as, an ironclad oath or pledge.
(n.) A naval vessel having the parts above water covered and protected by iron or steel usually in large plates closely joined and made sufficiently thick and strong to resist heavy shot.