phonebook vs telephone book

phonebook and telephone book both are nouns.

Word	Noun	Adjective	Verb	Adverb
phonebook	Yes	No	No	No
telephone book	Yes	No	No	No

As nouns, phonebook and telephone book are synonyms defined as:

phonebook and telephone book: a directory containing an alphabetical list of telephone subscribers and their telephone numbers

Other synonyms of phonebook include phone book, telephone directory.

phonebook (noun)	telephone book (noun)
a directory containing an alphabetical list of telephone subscribers and their telephone numbers	a directory containing an alphabetical list of telephone subscribers and their telephone numbers