vambrace(n = noun.artifact) lower cannon - cannon of plate armor protecting the forearm;
is a kind of cannon
is a part of body armor, body armour, cataphract, coat of mail, suit of armor, suit of armour

   The piece designed to protect the arm from the elbow to the wrist. [1913 Webster]

vambrace, n. hist. defensive armour for the forearm.

Etymology:
ME f. AF vaunt-bras, OF avant-bras f. avant before (see AVAUNT) + bras arm

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.