一刀[ittou] sword
一刀彫り[ittoubori] one-knife carving
一刀両断[ittouryoudan] cutting in two with a single stroke
印刀[intou] seal-engraving knife
円刃刀[enjintou] round-edged scalpel

快刀[kaitou] (literary) sharp sword
快刀乱麻[kaitouranma] solving a problem swiftly and skillfully
懐刀[futokorogatana] confidant
儀刀[gitou] ceremonial sword
軍刀[guntou] saber

鯔背[inase] gallant
違背[ihai] violation
棄背[kihai] giving up and turning back
向背[kouhai] one's attitude
上背[uwazei] stature

側背[sokuhai] flank
団栗の背比べ[dongurinoseikurabe] having no outstanding characteristics
中肉中背[chuunikuchuuzei] medium build
中背[chuuzei] average height
二律背反[niritsuhaihan] antinomy