ironclad adjective 4noun 3forms 3 adjective4 •Covered with iron, steel, or (loosely) any other tough metal; armor-plated.Unlike the average vehicle, cash delivery vans are ironclad and almost unstoppable. •(figurative) Solid or certain; not able to be disputed or questioned; irrefutable.The suspect had an ironclad alibi for his whereabouts on the night of the crime. •(figurative) Rigorous; severe; exacting.Observers of the day considered his rule more ironclad than that of the Prendergast machine in Kansas City, or even Tammany Hall in New York. — 1982 •(figurative) Stubborn; inflexible.He is in his seventieth year, and has done work enough in his life to try the most ironclad constitution. — 1893 noun3 •A ship, vessel, or vehicle with a covering of iron, steel, or (loosely) any other tough metal.He turned again to the nearest land ironclad, advancing now obliquely to him and not three hundred yards away, and then scrambled the ground over which he must retreat if he was not to be captured. — 1903 •An armor-plated warship, (especially) one preceding the invention of harveyized steel.About a couple of miles out lay an ironclad very low in the water, almost, to my brother's perception, like a water-logged ship. This was the ram Thunder Child. — 1898 •A wooden warehouse with an outer skin of corrugated metal. formsironclads · more ironclad · most ironclad