Definition
This is said when someone makes a statement that is very quickly proven wrong, often in an embarrassing way.
"I will never be late again," he said confidently. Famous last words! He was late again the next day.
She said she would never get back together with her ex-boyfriend. Famous last words! They were together again not long after.
"This can't possibly go wrong," the engineer said. Famous last words! The system crashed a few hours later.