The Collaborative International Dictionary of English v.0.48:

Yellow pages \Yel"low pag`es\, n. pl.
   a telephone book or part of a book in which the telephone
   numbers and often advertisements of business enterprises are
   listed in numerous sections, organized by the category of the
   business, the categories themselves being arranged
   alphabetically; a classified telephone directory. So called
   because for many years the listing thus organized was printed
   on yellow paper, to distinguish it from the white pages
   containing the names of individuals, listed alphabetically by
   last name. The yellow pages are usually bound together with
   the white pages in the telephone book distributed by the
   telephone company to its subscribers. The name was adopted by
   companies not affiliated with the telephone company, for the
   classified business directories that they sell.
   [PJC]

WordNet (r) 3.0 (2006):

yellow pages
    n 1: a telephone directory or section of a directory (usually
         printed on yellow paper) where business products and
         services are listed alphabetically by field along with
         classified advertising

Moby Thesaurus II by Grady Ward, 1.0:

20 Moby Thesaurus words for "Yellow Pages":
   Baedeker, bibliography, business directory, catalog, checklist,
   city directory, classified directory, directory, finding list,
   guidebook, handbook, handlist, index, itinerary, phone book,
   reference book, road map, roadbook, telephone book,
   telephone directory



The Free On-line Dictionary of Computing (30 December 2018):

Network Information Service
NIS
Yellow Pages

    (NIS) Sun Microsystems' Yellow Pages
   (yp) client-server protocol for distributing system
   configuration data such as user and host names between
   computers on a network.

   Sun licenses the technology to virtually all other Unix
   vendors.

   The name "Yellow Pages" is a registered trademark in the
   United Kingdom of British Telecommunications plc for their
   (paper) commercial telephone directory.  Sun changed the name
   of their system to NIS, though all the commands and functions
   still start with "yp", e.g. ypcat, ypmatch, ypwhich.

   Unix manual pages: yp(3), ypclnt(3), ypcat(1), ypmatch(1).

   (1995-04-08)