who‧dun‧it ,
whodunnit /ˌhuːˈdʌnət, ˌhuːˈdʌnɪt/
noun [countable] informal[
Date: 1900-2000;
Origin: who done it? 'who did it?']
a book, film etc about a murder case, in which you do not find out who killed the person until the end
[TahlilGaran] Dictionary of Contemporary English ▲