It means if they don’t repent that they are close to being cursed and will be burned.
1 Co 3: 14If any man’s work which he has built on it remains, he will receive a reward. 15If any man’s work is burned up, he will suffer loss; but he himself will be saved, yet so as through fire.
I have read at least a dozen different interpretations of this difficult verse from Paul many not having do with the issue at hand. It is beyond the scope of this forum to go over them and I don't want to hijack the thread so I'm going to leave it alone. I've got to believe Peter had verses like this in mind when he commented that in Paul's letters "there are some things hard to understand" (2 Peter 3:16) LOL.