Question

What does dead as a dumpling mean

Answer 1

It means the same thing as "dead as a doornail" completely dead. Dumplings aren't alive so they are "dead". So "dead as a dumpling" means to be completely dead, not alive in the slightest. 

Answer 2

To be " dead as a dumpling" means that you are very dead. It's an expression that you use to describe something or someone that you know for sure is dead.