What does "lost cause" mean?

A person or thing that is hopeless or futile.

What is a synonym for "lost cause"?

Common synonyms include: goner, goners.

name, noun

name, noun ·Rare ·Advanced level

Noun

1
A person or thing that is hopeless or futile. idiomatic
"He has already made up his mind, and it's a lost cause to try to change it."
2
a defeated cause or a cause for which defeat is inevitable wordnet

Proper Noun

1
The belief that the Confederate cause during the American Civil War was just and not related to slavery.
"Also implicit was the idea that all southerners accepted the basic tenets of the Lost Cause myth and concurred in this celebration of the Confederacy."

"He has already made up his mind, and it's a lost cause to try to change it."

From the generic term lost cause. The Confederacy was, of course, defeated.