Okay, so you know how when you're tired, you might lay down and just let your arms and legs rest and not move much at all? Well, the "Lazarus sign" is kind of like that- but a bit more serious.
Sometimes, when someone's body is really weak or sick, they might not be able to move their arms or legs like they normally would. And if they're REALLY weak or sick, they might not be able to move at all, even if they try really hard. This can happen if someone is really hurt or if they're really sick or if they're dying.
But in some rare cases, even when someone's body is super weak or sick, they might be able to move their arms or legs a little bit, without even meaning to. This movement is called the "Lazarus sign."
Doctors named it that after a guy named Lazarus in a story from a really old book. Basically, Lazarus was really sick and seemed like he was about to die. But then he got better suddenly and started moving around again- even though everyone thought he was going to die for sure.
So, even though the Lazarus sign sounds scary, it's actually kind of a hopeful thing sometimes. It means that even if someone's body is really weak or sick, they might still have a little bit of strength left to fight with. But doctors also know that if someone is showing the Lazarus sign, it means that they need a lot of help and medical attention right away.