What does lost cause mean?
A lost cause is a situation, goal, or person that will not succeed or improve despite all your efforts or assistance.
Most of his teachers gave up on him as a lost cause.
On a related note, if you can’t make up your mind if loss or lost is the word you need, remember that “loss” always functions as a noun.
You can use QuillBot’s free Paraphraser to help you find alternative ways of expressing “lost cause” in your specific context.