What is Fatal Error?
1.
Something your computer claims to have
"My computer just told me it had a fatal error, does that mean I'm going to die?"
See
2.
One careless mistake wrecking an otherwise flawless execution of some mischievous behavior.
Executor: "My parents would have never known my boyfriend was staying the night because he crept in really quietly but then my mom looked out the window and saw his truck!"
Friend: "Aw Fatal Error!"
See