Any feature that runs a program, etc. automatically.(noun)
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Use "autorun" in a sentence
"The Conficker virus can be spread by USB sticks especially if the system it plugs into has the 'autorun' feature enabled, which will run any executables - such as the virus - when the stick is plugged in."
"Clickfree's Transformer cable contains their backup and restore software, and uses the "autorun" feature of Microsoft Windows to automatically launch their backup / restore whenever the device is connected to your PC."
"How you could "in theory" install malicious software on a USB drive then have 'autorun' in windows install it automatically when plugged into a PC."