Noun. Alternative spelling: whodunnit. A whodunit is a narrative dealing with murder and the detection of the criminal - in other words a detective story. The term itself is, of course, an alteration of "who done it?" and according to Merriam-Webster's Collegiate Dictionary, it dates back to 1930.

Agatha Christie's Hercule Poirot and Miss Marple stories are classic whodunit examples.