I"ron*clad` (?), a. 1. Clad in iron; protected or covered with iron, as a vessel for naval warfare.

2. Rigorous; severe; exacting; as, an ironclad oath or pledge. [Colloq.]

I"ron*clad`, 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.

• Covered with iron.
  
• Solid or certain; not able to be disputed or questioned; irrefutable.
       The guy had an ironclad alibi for his whereabouts on the night of the crime.
  
• A ship or vessel covered in iron.