Butt Phone 

A butt phone is a device used by technicians (and rarely ever home users) working on telecommunications networks to diagnose issues within the communications systems.

All the numbered buttons and the plugs etc are located on the end of the handset itself. Hence, the term butt phone.

Example 1:
Technician: "I have my butt plugged into the line"

Example 2:

Technician: "I love my butt phone"

Butt Phone by HotWater May 21, 2012

Phonebook Butt

A posterior so large, when the subject is seated, they appear to be taller. Like a child sitting on a phone book.

Have you seen Jessa’s butt? She’s got a phonebook butt!

Phonebook Butt by Dr. Knockers January 3, 2023

Buttphone 

A buttphone is a (usually) small cellphone smuggled into prison inside an inmates rectal cavity (aka his "PK holder, aka his "Pooey Vuitton")

Inmate 1: "Yo, where's Lefty at?"
Inmate 2: "He's in his house, talkin' with his girl on the Buttphone. I'm keeping six."

Buttphone by 806997F May 3, 2018