含义:粗略的、快速估算的(通常指未经详细计算的草稿)。
例句:It was just a back-of-the-envelope calculation, not meant to be precise.
含义:非常偏远、荒凉的地方;天涯海角。
例句:They live in the back of beyond—there’s no cell service for miles!
含义:潜意识里;隐隐约约记得或担心某事。
例句:I had a nagging worry at the back of my mind all day.
含义:对某事非常熟悉(常用于“know like the back of your hand”)。
例句:She knows this city like the back of her hand.