Radio Frequency Interference Hear it!

Radio Frequency Interference (RFI) Hacker Definition
Also known as electromagnetic interference. Electric circuits that carry rapidly changing signals, such as data lines, emit an electromagnetic signal. This signal can interfere with—or disturb—signals on other lines. This physical property can be abused by crackers (more properly called phreakers) to block or slow down the communication infrastructure of a target.
Radio Frequency Interference (RFI) Telecom Definition
See RFI.