Definition of "sourcebook"

sourcebook

noun
plural sourcebooks
1. A book consisting of a collection of writings on a particular subject.
2. (video games) A publication intended to supplement the core materials of a roleplaying game.
  Quotations
  That sourcebook is aimed at players of fighters, rogues, rangers, and warlords, and by design you're not going to find much in that book to appeal to other characters.
  2008, James Wyatt, Bill Slavicsek, Richard Baker, Dungeon Master 4th Edition For Dummies, page 156