字典解释

“fathom“既是名词也是动词。作为名词，fathom 表示测量水深的单位“英寻”；作为动词，它表示“透彻理解”“深入了解”，今天我们要学习的是它的动词用法。和表示“理解”的常见词（比如 understand，comprehend，figure out）相比，fathom 有“深不可测”“绞尽脑汁也没有想透”的意味，在一些语境下使用 fathom 会更准确，在写作和口语中都可以使用。

例句

比如，有首老歌叫《女孩的心思你别猜》，说的也就是有些女孩的行为叫人难以看透，我们可以用 fathom 造句：
Girl’s behaviors/intentions are often hard to fathom.

在口语表达中，难以看透某人或某事也可以直接说“I can’t fathom him/her/it”。再比如我们常说“问世间情为何物，直教人生死相许”，是不是也可以解读为：
It’s hard to fathom why people fall in love and how some of them would die for the one they love.

《经济学人》中的例子
Higher barriers to trade will add to inflation and hurt GDP, but to an extent that is hard to fathom.

Of all the Trump administration’s many regulatory cuts, the unrolling of these modest improvements to school food is among the hardest to fathom.

翻译练习

我们难以理解“无条件的爱”意味着什么
It is hard to fathom what the meaning of “love without requirement”.

参考翻译
What 'sunconditional love' truly means is hard to fathom.

或者
It's hard to fathom what it means to love someone unconditionally.