English version comes after Japanese.
「キャスティングボード」ってたまに聞きますが、ボードではありません。「ボート」でもない。英語で書くと「Casting Vote」で「議長決裁」と訳されます。議会で可否同数になった場合に、議長が議案の可否を決めることを言います。カタカナにされると分からなくなりますね。
The word "Casting Vote" is used in ordinary conversations but it doesn't seem people understand what it means. Many Japanese people probably think it's a "boat" or "board" because it's difficult to show the "V" sound when it's written in Japanese. You might want to tell them it's a "vote" if somebody uses the word to you.