ironclad(n = noun.artifact) - a wooden warship of the 19th century that is plated with iron or steel armor;
is a kind of combat ship, war vessel, warship

1.  ironclad(s = adj.all) - sheathed in iron plates for protection;

2.  ironclad(s = adj.all) brassbound - inflexibly entrenched and unchangeable; "brassbound traditions"; "brassbound party loyalists"; "an ironclad rule"

1.  Clad in iron; protected or covered with iron, as a vessel for naval warfare. [1913 Webster]

2.  Rigorous; unbreakable; severe; exacting; inflexible; as, an ironclad oath or pledge. [1913 Webster]

   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. Modern naval vessels are made of steel throughout, and this term is only used in historical contexts. [1913 Webster]

1.  having an outer covering of iron or steel; as, an ironclad war vessel. [PJC]

2.  so strong or secure as to be unbreakable; as, an ironclad contract. [PJC]

ironclad, adj. & n.
--adj.
1 clad or protected with iron.
2 impregnable; rigorous.
--n. hist. an early name for a 19th-c. warship built of iron or protected by iron plates.

N  defense, protection, guard, ward, shielding, propugnation, preservation, guardianship, area defense, site defense, self-defense, self-preservation, resistance, safeguard, balistraria, bunker, screen, camouflage, fortification, munition, muniment, trench, foxhole, bulwark, fosse, moat, ditch, entrenchment, intrenchment, kila, dike, dyke, parapet, sunk fence, embankment, mound, mole, bank, sandbag, revetment, earth work, field- work, fence, wall dead wall, contravallation, paling, palisade, haha, stockade, stoccado, laager, sangar, barrier, barricade, boom, portcullis, chevaux de frise, abatis, abattis, abbatis, vallum, circumvallation, battlement, rampart, scarp, escarp, counter-scarp, glacis, casemate, vallation, vanfos, buttress, abutment, shore, breastwork, banquette, curtain, mantlet, bastion, redan, ravelin, vauntmure, advance work, horn work, outwork, barbacan, barbican, redoubt, fort-elage, fort-alice, lines, loophole, machicolation, sally port, hold, stronghold, fastness, asylum, keep, donjon, dungeon, fortress, citadel, capitol, castle, tower of strength, tower of strength, fort, barracoon, pah, sconce, martello tower, peelhouse, blockhouse, rath, wooden walls, bulletproof vest, armored vest, buffer, corner stone, fender, apron, mask, gauntlet, thimble, carapace, armor, shield, buckler, aegis, breastplate, backplate, cowcatcher, face guard, scutum, cuirass, habergeon, mail, coat of mail, brigandine, hauberk, lorication, helmet, helm, bassinet, salade, heaume, morion, murrion, armet, cabaset, vizor, casquetel, siege cap, headpiece, casque, pickelhaube, vambrace, shako, bearskin, panoply, truncheon, garrison, picket, piquet, defender, protector, guardian, bodyguard, champion, knight-errant, Paladin, propugner, bulletproof window, hardened site, defending, defensive, mural, armed, armed at all points, armed cap-a-pie, armed to the teeth, panoplied, iron-plated, ironclad, loopholed, castellated, machicolated, casemated, defended, proof against, armored, ballproof, bulletproof, hardened, defensively, on the defense, on the defensive, in defense, at bay, pro aris et focis, Int, no surrender!, defense not defiance, Dieu defend le droit, fidei defensor, defender of the faith.

N  combatant, disputant, controversialist, polemic, litigant, belligerent, competitor, rival, corrival, fighter, assailant, champion, Paladin, mosstrooper, swashbuckler fire eater, duelist, bully, bludgeon man, rough, prize fighter, pugilist, boxer, bruiser, the fancy, gladiator, athlete, wrestler, fighting-cock, game-cock, warrior, soldier, fighting man, Amazon, man at arms, armigerent, campaigner, veteran, swordsman, sabreur, redcoat, military man, Rajput, armed force, troops, soldiery, military forces, sabaoth, the army, standing army, regulars, the line, troops of the line, militia, yeomanry, volunteers, trainband, fencible, auxiliary, bersagliere, brave, garde-nationale, garde-royale, minuteman, auxiliary forces, reserve forces, reserves, posse comitatus, national guard, gendarme, beefeater, guards, guardsman, yeomen of the guard, life guards, household troops, janissary, myrmidon, Mama, Mameluke, spahee, spahi, Cossack, Croat, Pandoz, irregular, guerilla, partisan, condottiere, franctireur, tirailleur, bashi-bazouk, vietminh, vietcong, shining path, contras, huk, hukbalahap, mercenary, soldier of fortune, hired gun, gunfighter, gunslinger, bushwhacker, free lance, companion, Hessian, hit man torpedo, soldier, levy, draught, Landwehr, Landsturm, conscript, recruit, cadet, raw levies, infantry, infantryman, private, private soldier, foot soldier, Tommy Atkins, rank and file, peon, trooper, sepoy, legionnaire, legionary, cannon fodder, food for powder, officer, subaltern, ensign, standard bearer, spearman, pikeman, spear bearer, halberdier, lancer, musketeer, carabineer, rifleman, jager, sharpshooter, yager, skirmisher, grenadier, fusileer, archer, bowman, horse and foot, horse soldier, cavalry, horse, artillery, horse artillery, light horse, voltigeur, uhlan, mounted rifles, dragoon, hussar, light dragoon, heavy dragoon, heavy, cuirassier, Foot Guards, Horse Guards, gunner, cannoneer, bombardier, artilleryman, matross, sapper, sapper and miner, engineer, light infantry, rifles, chasseur, zouave, military train, coolie, army, corps d'armee, host, division, battalia, column, wing, detachment, garrison, flying column, brigade, regiment, corps, battalion, sotnia, squadron, company, platoon, battery, subdivision, section, squad, piquet, picket, guard, rank, file, legion, phalanx, cohort, cloud of skirmishers, war horse, charger, destrier, marine, man-of-war's man, navy, wooden walls, naval forces, fleet, flotilla, armada, squadron, man-of-war, destroyer, submarine, minesweeper, torpedo-boat, torpedo-destroyer, patrol torpedo boat, PT boat, torpedo- catcher, war castle, H, M, S, battleship, battle wagon, dreadnought, line of battle ship, ship of the line, aircraft carrier, carrier, flattop, helicopter carrier, missile platform, missile boat, ironclad, turret ship, ram, monitor, floating battery, first- rate, frigate, sloop of war, corvette, gunboat, bomb vessel, flagship, guard ship, cruiser, armored cruiser, protected cruiser, privateer, tender, store ship, troop ship, transport, catamaran, merchant marine.

N  covering, cover, baldachin, baldachino, baldaquin, canopy, tilt, awning, tent, marquee, tente d'abri, umbrella, parasol, sunshade, veil (shade), shield, roof, ceiling, thatch, tile, pantile, pentile, tiling, slates, slating, leads, barrack, plafond, planchment, tiling, shed, top, lid, covercle, door, operculum, bulkhead, bandage, plaster, lint, wrapping, dossil, finger stall, coverlet, counterpane, sheet, quilt, tarpaulin, blanket, rug, drugget, housing, antimacassar, eiderdown, numdah, pillowcase, pillowslip, linoleum, saddle cloth, blanket cloth, tidy, tilpah, apishamore, integument, tegument, skin, pellicle, fleece, fell, fur, leather, shagreen, hide, pelt, peltry, cordwain, derm, robe, buffalo robe, cuticle, scarfskin, epidermis, clothing, mask, peel, crust, bark, rind, cortex, husk, shell, coat, eggshell, glume, capsule, sheath, sheathing, pod, cod, casing, case, theca, elytron, elytrum, involucrum, wrapping, wrapper, envelope, vesicle, corn husk, corn shuck, dermatology, conchology, testaceology, inunction, incrustation, superimposition, superposition, obduction, scale, veneer, facing, overlay, plate, silver plate, gold plate, copper plate, engobe, ormolu, Sheffield plate, pavement, coating, paint, varnish, plating, barrel plating, anointing, enamel, epitaxial deposition, vapor deposition, ground, whitewash, plaster, spackel, stucco, compo, cerement, ointment, covering, superimposed, overlaid, plated, cutaneous, dermal, cortical, cuticular, tegumentary, skinny, scaly, squamous, covered, imbricated, loricated, armor plated, ironclad, under cover, cowled, cucullate, dermatoid, encuirassed, hooded, squamiferous, tectiform, vaginate.