n.擊穿；飛弧；嚴重打火

動詞arc的現(xiàn)在分詞.

The sun appears to move in an arc across the sky. 太陽看起來在天空以弧線運行。

An early instrument for measuring altitude of celestial bodies, consisting of a90= graduated arc with a movable radius for measuring angles. 象限儀用來測量天體緯度的一種早期工具，由一個有90度刻度的圓弧和一個用來測量角度的可移動的半徑構(gòu)成