1. Inflexibly entrenched and unchangeable; SYN. brassbound.
2. Without flaws or loopholes; SYN. unassailable, unshakable, watertight.

An armored naval vessel especially of the mid to late 19th century.
Wooden warship covered with armor plate. The first to be constructed was the French Gloire 1858, but the first to be launched was the British HMS Warrior 1859. The first battle between ironclads took place during the American Civil War, when the Union Monitor fought the Confederate Virginia (formerly the Merrimack) 9 March 1862. The design was replaced by battleships of all-metal construction in the 1890s.
The US Navy's Great White Fleet was especially well known.