"어림없다" is used to describe something that you can't do no matter how many times you try, or no matter what happens. It can be translated as "Far from it"/ "~far beyond"/ "Absurd". Here are some examples to help you understand. Ex) "그것은 내 힘으로는 어림없다." = This work is far beyond my capacity. " 어림없어" = Don't you wish. "어림없는 소리마. = Don't say anything absurd.

What a thing to say!/Absurd!/Impossible!/Far from it!

To help with understanding, 어림 means "rough guess" or "quick estimate". So the word literally means, it is so far off the mark no estimation is even possible. From that comes the meanings like impossible, far from it, no chance, absurd, etc.