Clad in iron; protected or covered with iron, as a vessel for naval warfare.
Rigorous; severe; exacting; as, an ironclad oath or pledge.
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.
2011 adventure film directed by Jonathan English
2009 video game
Ironclad in Spanish is Acorazado