who's who

Short definition from Wiktionary

Noun

1. 1
   A publication containing biographies of well-known or important people.
2. 2
   A list of notable, famous, or upper-class people.
3. 3
   Collectively, the elite class.
4. 4
   A person appearing in a Who's Who publication.
5. 5
   A celebrity or famous person, someone likely to be in such a publication.
6. 6
   The identities of specific people, understood in terms of such distinguishing characteristics as their backgrounds, prominence, achievements, jobs, etc., as a basis for comparing them and especially as a basis for ranking them within a social group.
7. 7
   Alternative form of who's who.