phonebook /ˈfoʊnˌbʊk/noun 2verb 1forms 3 noun2 •A directory of all the phone numbers used in a district.One even proposes, in a workaday monotone, that the first hundred people in any Idaho phonebook could do just as well as the legislators at making decisions in the capital. — 2007 •A large lookup table.He does this by using the Domain Name System, or DNS, which is the phonebook for the Internet. — 2007 verb1 •To determine the identity of (an Internet user) by comparing personal information to real-world directories or databases (e.g., lists of people in phonebooks or relatives of those who have recently died). formsphonebooked · phonebooking · phonebooks