がちんこ

noun

head-to-head; serious competition; real fight

Slang term for a serious, no-holds-barred contest, originally from sumo but now used broadly for any earnest competition or showdown.

• 今こん夜やはがちんこで勝しょう負ぶしよう。

  Let's have a real fight tonight.

• あの二人ふたりの議ぎ論ろんは完かん全ぜんにがちんこだった。

  That argument between the two was a total head-to-head.