1. A reference work containing concise biographical sketches of well-known people.
2. Well-known people in a particular profession, region, etc.

ETYMOLOGY: The first Who's Who was published in the UK in 1849. Now the term is in wider use and there are thousands of specialized Who's Whos publications, for high school students, for Nebraskans, and for the dead (Who Was Who). There's even a Who's Who in Hell. Earliest documented use of the generic use of the term is from 1917.

WHO'S WHOM - a compendium of pseudo-intellectuals, like the lady in Sinclair Lewis' Main Street who referred to the common folk as "wa pollwa" because she had once read the term "hoi polloi" and thought it was French