英语口语：“难以用语言表达”用英语怎么说呢?

Je ne sais quoi is something that cannot be adequately described or expressed.

不可言说指无法用语言充分表达的某物。

Je ne sais quoi是法语“我不知道是什么”的意思，这个词表达的不可言说之物多为褒义。

Example：

Although the sculpture had flaws, it also had a certain je ne sais quoi that made it very appealing.

尽管这尊雕塑有瑕疵，但某种无法言说的东西赋予了它魅力。