who's who

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun uncountable, capitalized A publication containing biographies of well-known or important people.
• noun uncountable A list of notable, famous, or upper-class people.
• noun uncountable Collectively, the elite class.
• noun countable A person appearing in a Who's Who publication.
• noun countable A celebrity or famous person, someone likely to be in such a publication.
• noun uncountable, idiomatic 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.