Definitions Us noun
Informal a mystery novel, play, etc.
Webster’s New World College Dictionary, Fourth Edition, compiled by the
editors of Webster’s New World Dictionaries. Copyright © 2010 by Houghton
Mifflin Harcourt. Published by Houghton Mifflin Harcourt. All rights reserved.
Word origin of 'whodunit'< who + do1 verb:transitive + it1: coined (1930) by D. Gordon in American News of Books