A repetition of a signal in a communications line. The difference in electrical characteristics at opposite ends can cause the echo.
In communications, to transmit received data back to the sending station allowing the user to inspect visually what was received. A local echo displays what you type on your screen.
(Echo) Amazon's Bluetooth speaker, music streamer and virtual assistant. See Amazon Echo
A DOS, Windows and OS/2 screen command that displays messages and turns off/on screen responses. See batch file abc's