The effect is almost impossible to describe.

这影响几乎无法言表。

《柯林斯英汉双解大词典》

It is impossible to describe it, you must picture it to yourself.

这是无法描述的，你必须自己想象它。

youdao

What our poor friend has to bear is impossible to describe.

我们那可怜的朋友所忍受的痛苦是无法描述的。

youdao

A fight followed and a confusion of sounds impossible to describe.

VOA: special.2011.02.26

Margaret Smith, a leader in Washington society at that time, wrote a letter describing the scene: Ladies fainted, men were seen with bloody noses and such a scene of confusion took place as is impossible to describe - those who got in could not get out by the door again, but had to scramble out of windows.

VOA: special.2009.01.19

Afterwards he found it almost impossible to describe the experience that sent him running in anguish down the rocky hillside to his wife.

NPR: Armstrong, 'Muhammad: A Prophet for Our Time'

The feeling of being in solitary is almost impossible for him to describe.

CNN: No kid should be in solitary confinement

It is impossible for us to perfectly describe the state of anything at any time.

FORBES: Computing Desire