Backing vacuum
[化] 前级真空
🧩 词语组成解析
backing
[['bækiŋ]]
n. 后退, 衬背, 后援, 支持者\\n[化] 衬垫
🗣️ 情景例句
You won't believe this,
简直不会相信，
I can't believe it!
简直无法相信！
and we have to lower into the ground and haul out of the ground great lengths of drill pipe which are rotated by an engine at the top and are fitted with a cutting bit at the bottom.
我们必须把很长的钻杆一节节地钻入地下，然后再从地下拉出来。钻杆顶部安装的发动机带动钻杆旋转，它的底部装有钻头。