Double kill: A play in which two outs are made with one pitch.

双杀：用一次投球使二人同时出局。

My extension is two four double 0 (2400).

我的分机号是2400。

Since technology is a double-edged sword, the development it brings and its potential threats are two sides of the same coin.

技术是一把双刃剑，因此它所带来的发展及其潜在威胁是紧密相关的。

Let us look at an idiom: kill two birds with double-edged sword.

我们再看一个成语：一举两得/一箭双雕。

To illustrate this, suppose you have two double arrays a and b and want to create a third array x such that x=a+b.

为了展示这一点，假设您有两个双精度的数组 a 和 b，并且要创建第三个数组 x，比如 x=a+b。