arc
/ɑ:k; ɑrk/ n
1 part of the circumference of a circle or some other curved line 弧（圆周或其它曲线的一部分）. =>illus at circle 见circle之插图.
2 thing with this shape 弧形物
the arc of a rainbow 虹的弧形.
3 luminous electric current passing across a gap between two terminals 电弧; 弧光. arc, v (pt, pp arced / ɑ:kt; ɑrkt/, pres p arcing/ ˈɑ:kɪŋ; `ɑrkɪŋ/) [I]
form an electric arc 形成电弧; 产生弧光.