You can think of one thin bar held up between two posts, going up a little after every round. Everyone who gets over stays in; the moment you cannot get over, you are out. The words name that whole event, which is why they nearly always come with the — it is a fixed thing with rules, not simply the act of jumping high.
可以想成兩根柱子中間架著一根細細的橫桿，每跳完一輪就往上升一點。過得去的人留下來，過不去的那一刻就出局。這兩個字指的是「整個項目」，所以前面幾乎一定帶 the——它是一件有規則的固定事情，不是隨口說的「跳得高」。
From the word’s history
The supplied source records the word as high + jump, so the name says exactly what happens: a jump measured by height.
手上的資料把這個詞記為 high 加 jump 合成，所以名字本身就把事情說完了：用高度來比的一種跳。
Wiktionary, "high jump"