Definitions for whodunithuˈdʌn ɪt
Random House Webster's College Dictionary
a narrative of a murder or a series of murders and the detection of the criminal; detective story.
Origin of whodunit:
1925–30; jocular formation from Who done it?, for standard E Who did it?
mystery, mystery story, whodunit(noun)
a story about a crime (usually murder) presented as a novel or play or movie
A novel or drama concerning a crime (usually a murder) in which a detective follows clues to determine the perpetrator.
Origin: Alteration of who done it?