看着太阳爬上山冈，这几乎是一种难以言传的体验。

Watching the sun rise over the mountain was an almost mystical experience.

《牛津词典》

快乐越是纯净，就越是难以言传。

The purer the happiness, the less communicable it is.

youdao

从人生各种意义来看，美是难以言传的。

Beauty is in the terms of human meanings is meaningless.

youdao

And even more important, Lycidas will continue to sing in heaven just as he had sung on earth, except now he can hear the unexpressive - that means "inexpressible" -- nuptial song.

更重要的是，利西达斯在天堂依旧会唱歌,正如他在人间唱歌一样，除了现在他听到的是unexpressive的,-意思是“难以言传的“--婚礼之歌。

耶鲁公开课 - 弥尔顿课程节选